Search PubMed⌕ Search

Biomedical subjects

G Thibault

Publications and source records attributed to G Thibault.

At least 55 records · Page 3Linked to original sources
PubMed1996

Specific potentiation by cyclic AMP of natriuretic peptide-mediated cyclic GMP production in adipose tissue.

Adipose tissue of the mesenteric territory contains large quantities of natriuretic peptide receptors (NPR) mainly of the NPR-C subtype. Guanylyl cyclase-bound receptors are also present since atrial natriuretic peptide (ANP) and C-type natriuretic peptide (CNP) are equally potent in activating this enzyme. While searching for a potential biological role for NP in adipocytes we observed that ANP-mediated generation of cyclic GMP (cGMP) was potentiated when the cells were simultaneously treated with isoproterenol. Indeed, isoproterenol, a beta-adrenergic agonist, and forskolin, an activator of adenylyl cyclase, can both double or triple cGMP production in response to ANF stimulation. There was a direct correlation between the level of cyclic AMP (cAMP) generated and the level of NP-mediated cGMP production suggesting that a cAMP-dependent mechanism may be responsible of this potentiation. To determine whether or not this phenomenon was unique to adipocytes, NPR subtypes were characterized in 4 established cell lines and their cAMP-dependent cGMP behavior examined. A10 and A7r5 smooth muscle cells showed identical ratio of NPR subtypes with about 95% NPR-C and 5% NPR-B. PC12 cells presented 100% NPR-A and NIH 3T3 fibroblasts 50% NPR-C and 50% NPR-B. Regardless of the NPR subtype, forskolin could not potentiate the cGMP generation in these cell lines. These data indicate that the cAMP-dependent potentiation of the NP-mediated cGMP production is unique to adipocytes, appears independent of the guanylyl cyclase-linked NPR subtypes and may be involved in the sensitization of the guanylyl cyclase domain of NPR for a potential biological role of NP in the adipose tissue.

3T3 Cells↗
PubMed1996

Inducible nitric oxide synthase in vascular smooth muscle cells from prehypertensive spontaneously hypertensive rats.

The inducible nitric oxide synthase (iNOS) present in vascular smooth muscle cells (VSMC) may play a role in the generation of nitric oxide (NO) in the vascular wall, regulating blood vessel tone in normotension and hypertension. In this study the effect of interleukin (IL)-1 beta, a cytokine that induces iNOS, on NO generation (measured as nitrite), cyclic guanosine monophosphate (cGMP) generation, and steady-state abundance of iNOS mRNA were examined in VSMC from 3 week old spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats, during the period preceding the elevation of blood pressure. With cell density dependent variations in nitrite production eliminated, VSMC from SHR and WKY did not differ in NO generation except after prolonged incubation (30 h), when SHR cells produced less NO. However, cGMP concentrations associated with IL-1 beta stimulation were significantly smaller in SHR VSMC than in cells from WKY. IL-1 beta stimulation resulted in increased abundance of iNOS mRNA to the same extent in both WKY and SHR VSMC. Inhibitors of NOS, NG-monomethyl-L-arginine (L-NMMA) and N omega-nitro-L-arginine methyl ester (L-NAME), did not block the induction of iNOS mRNA, although nitrite production and cGMP generation were inhibited. The protein synthesis inhibitor cycloheximide and the RNA synthesis inhibitor actinomycin-D almost completely blocked the production of nitrite in cells from both strains of rats. Actinomycin-D completely blocked the induction of iNOS mRNA by IL-1 beta in cells from both strains of rats, whereas cycloheximide partially blocked its synthesis in WKY, but had no significant effect on IL-1 beta induced expression of iNOS mRNA in SHR VSMC. Thus, IL-1 beta controls iNOS gene expression at the transcriptional level, and an intermediate labile protein, whose synthesis is inhibited by cycloheximide, is required for IL-1 beta stimulated induction of iNOS mRNA transcription in WKY cells but not in SHR. We conclude that although iNOS is expressed to similar extent in VSMC of prehypertensive SHR and WKY and similar amounts of NO are initially generated, there are differences between the VSMC of SHR and WKY in the regulation of the transcription of iNOS mRNA, there is a lower sustained production of NO, and there is a reduced generation of cGMP in response to IL-1 beta stimulated NO production. These differences between VSMC from prehypertensive SHR and WKY may indicate a pathophysiological role of iNOS in early blood pressure elevation in SHR.

Animals↗
PubMed1996

Human lymphocyte adhesion to xenogeneic porcine endothelial cells: modulation by human TNF-alpha and involvement of VLA-4 and LFA-1.

Considering that in the allogeneic situation the adhesion of recipient lymphocytes to donor endothelial cells initiates the cellular rejection, we questioned the possible occurrence of a similar process in the xenogeneic situation. The adhesion of human peripheral blood lymphocytes (PBL) to porcine aortic endothelial cells (PAEC) was thus studied in an in vitro porcine-to-human xenogeneic model. It was found that 25.9% of human PBL adhered to resting PAEC. Furthermore, this adhesion increased significantly when the PAEC were stimulated by the human cytokine TNF-alpha (tumor necrosis factor-alpha). The effect of human TNF-alpha was concentration- and time-dependent and was maximal (from 25.9% to 35.6%) with 100 U/ml during 6 h. Moreover, blocking experiments with monoclonal antibody (mAb) demonstrated the role of the PBL adhesion molecules LFA-1 and especially VLA-4. Indeed, an anti-CD11a mAb decreased PBL adhesion to resting PAEC by 17.1% and to TNF-alpha stimulated PAEC by 16.9%, whereas an anti-CD49d mAb decreased dramatically PBL adhesion to resting PAEC by 53.1% and to TNF-alpha stimulated PAEC by 41.0%. Finally, phenotypic analysis of the adherent PBL showed that 50.5% of adherent cells to resting PAEC were NK (natural killer) cells, whereas 50.7% of adherent cells to TNF-alpha stimulated PAEC were T lymphocytes, showing the preferential adhesion of NK cells to resting PAEC, and that the stimulation of the PAEC with human TNF-alpha affects predominantly T lymphocyte adhesion. These results indicate that human PBL could bind to xenogeneic PAEC and that this interaction could be a first step of a xenogeneic cellular rejection.

Animals↗
PubMed1996

Human NK cell-mediated direct and IgG-dependent cytotoxicity against xenogeneic porcine endothelial cells.

Once hyperacute rejection has been prevented, the pig-to-human xenograft might be exposed to vascular cell-mediated rejection directed against vascular structures. In order to evaluate the relative importance of direct and antibody-dependent anti-endothelial cell-mediated cytotoxicity in different individuals, freshly isolated human blood leukocytes were incubated with confluent porcine aortic endothelial cells (PAEC) in a 4 h Cr-release cytotoxicity assay. Peripheral blood mononuclear cells (PBMC) and lymphocytes (PBL) of all subjects tested (but not monocytes or neutrophils) directly killed PAEC, with wide interindividual variations (from 2.8% to 32%). The addition of heat-inactivated autologous serum to PBMC and PBL (but not to myeloid cells) always enhanced cytotoxicity. This antibody-dependent cell-mediated cytotoxicity (ADCC) was also observed in the presence of adult pooled serum and cord blood pooled serum and was eliminated after adsorption of adult pooled serum to insoluble protein A, demonstrating that IgG is the only class of immunoglobulin involved in this phenomenon. Moreover, blocking Fc gamma RIII with an anti-CD16 mAb eliminated ADCC without affecting direct cytotoxicity. When the ADCC exerted by the PBL of all subjects was assessed with the same preparation of purified IgG, wide interindividual variations were again observed. Surprisingly, there was no correlation between direct cytotoxicity and ADCC although, as depletion experiments demonstrated, both were due to CD16+ natural killer (NK) cells. These results argue that CD16+ NK cells could play an important role in early vascular rejection of porcine discordant xenografts, by both a direct and an IgG xenoreactive natural antibody-dependent cell-mediated cytotoxicity.

Animals↗
PubMed1996

Docosahexaenoic and eicosapentaenoic acids inhibit human lymphoproliferative responses in vitro but not the expression of T cell surface activation markers.

The effects of polyunsaturated fatty acids (PUFAs: docosahexaenoic (DHA) and eicosapentaenoic (EPA) acids) on induced lymphocyte proliferation and expression of CD25alpha chain of interleukin-2 receptor, CD71 and HLA-DR were investigated. PUFAs had no effect on phytohaemagglutinin (PHA)-induced lymphocyte agglutination, but they strongly inhibited the lymphoproliferative response to PHA. This inhibitory effect is PUFA dose-dependent and seems to be more potent with DHA than EPA, Pre-incubation experiments showed that lymphocytes cultured with PUFAs for 6 h then washed and exposed to PHA, still inhibited lymphocyte proliferation. The authors also showed that this inhibitory activity was time dependent but became nonsignificant when PUFAs were added after 48 h lymphocyte culture. The addition of excess exogenous human recombinant rIL-2 partly restored PHA-lymphocyte proliferation inhibited by EPA but not by DHA. On the other hand, the authors showed that PUFAS did not inhibit IL-2 stimulated lymphocyte proliferation. The addition of PUFAs to cell culture medium had no inhibitory action on the PHA-induced lymphocyte expression of CD25, CD71 and HLA-DR. Furthermore, this effect appeared independent of eicosanoid synthesis or peroxide formation. Indeed, the inclusion of aspirin and vitamin E in the culture medium did not prevent the inhibitory effects of PUFAs on lymphocyte proliferation. Regardless of the mechanism of action, the inhibitory effect of PUFAs on activated lymphocytes may explain why some clinical trials of fish oil supplemented diets containing high amounts of DHA and EPA have been successful in improving the health status of patients suffering from inflammatory and autoimmune disorders.

Adult↗
PubMed1996

Immunoactive products of placenta. V. Immunoregulatory properties of a low molecular weight compound obtained from human placental cultures.

PROBLEM: We have previously shown that supernatants from short-term cultures of human placental explants (HPS) are immunosuppressive in vitro as well as in vivo. They contain a low M.W. factor endowed with immunoregulatories activities (Filtrate of such with a 5 kDa cut off). In this paper, we wanted to assess whether this low M.W. material accounts for most, if not all, of the immunosuppressive properties of crude HPS and begin to investigate its mode of action. RESULTS: The filtrate is active across species barrier and inhibits human and murine PHA driven lymphocyte proliferation, Mixed Lymphocyte Reaction, and Natural Killer activity as did crude HPS. It does not affect CTL lytic function at effector stage. Its cross species activity allowed us to study its effects in vivo. It corrects resorbtions in the CBA x DBA/2 murine spontaneous abortion model, and suppresses local and general GVH reactions in a model (A cells into irradiated A x B Fls) relevant to a clinical use e.g., bone marrow transplantation. To ensure that such survival of the recipients was due to donor cells in the latter, surviving experimental animals were analysed by FACS for repopulating lymphocytes phenotype, which was indeed of donor origin. To elucidate the mechanism(s) of action of the active HPS moiety, we first tested various malignant cell lines for the minimal incubation time required for maximal lymphocyte inhibition. In the same vein, we verified that lymphocytes stimulated by PHA and simultaneously treated with filtrate were unresponsive to a second PHA challenge. The effects of the material was reversible if cells were washed out of it early enough before otherwise entering a cycle leading ultimately to cell death in vitro. Finally, we tested several second messenger pathways, none of which were modified. CONCLUSION: These data suggest that the filtrate contains an entity that represents the main, if not all, the immunosuppressive molecules present in HPS. In addition, they suggest that the material acts only on activated T cells and requires to be present early in the replication activation cycle. Altogether, the in vitro data strongly suggest that the material is acting by inducing clonal deletion in activated (T) cells.

Animals↗
PubMed1996

Modulation of Ca2+ transients in neonatal and adult rat cardiomyocytes by angiotensin II and endothelin-1.

Vasoactive peptides may exert inotropic and chronotropic effects in cardiac muscle by modulating intracellular calcium. This study assesses effects of angiotensin II (ANG II) and endothelin-1 (ET-1) on intracellular free calcium concentration ([Ca2+]i) in cultured cardiomyocytes from neonatal and adult rats. [Ca2+]i was measured microphotometrically and by digital imaging using fura 2 methodology. Receptor subtypes through which these agonists induce responses were determined pharmacologically and by radioligand binding studies. ANG II and ET-1 increased neonatal atrial and ventricular cell [Ca2+]i transients in a dose-dependent manner. ANG II (10(-11) to 10(-7) M) failed to elicit [Ca2+]i responses in adult cardiomyocytes, whereas ET-1 increased [Ca2+]i in a dose-dependent manner. The ETA receptor antagonist BQ-123 significantly reduced (P < 0.05) ET-1 induced responses, and the ETB receptor agonist IRL-1620 (10(-7) to 10(-5) M) significantly increased (P < 0.05) [Ca2+]i in neonatal and adult cardiomyocytes. ET-1 binding studies demonstrated 85% displacement by BQ-123 and approximately 15% by the ETB receptor agonist sarafotoxin S6c, suggesting a predominance of ETA receptors. Competition binding studies for ANG II failed to demonstrate significant binding on adult ventricular myocytes, indicating the absence or presence of very few ANG II receptors. These data demonstrate that ANG II and ET-1 have stimulatory [Ca2+]i effects on neonatal cardiomyocytes, whereas in adult cardiomyocytes, ANG II-induced effects are insignificant, and only ET-1-induced responses, which are mediated predominantly via ETA receptors, are preserved. Cardiomyocyte responses to vasoactive peptides may thus vary with cardiac development.

Age Factors↗
PubMed1996

Cytosolic calcium changes induced by angiotensin II in neonatal rat atrial and ventricular cardiomyocytes are mediated via angiotensin II subtype 1 receptors.

We determined the effects of angiotensin II (Ang II) on cytosolic free calcium concentrations ([Ca2+]i) in the absence and presence of the selective angiotensin subtype 1 (AT1) receptor antagonist losartan or the selective AT2 antagonist PD 123319 in cultured neonatal rat atrial and ventricular cardiomyocytes. We also Ang II receptor density, affinity, and mRNA expression. [Ca2+]i was measured in single cells microphotometrically and by fluorescent digital imaging with fura 2 methodology. Receptor parameters were assessed by competitive binding studies with 125I-[Sar1,Ile8]Ang II in the presence of increasing concentrations of [Sar1,Ile8]Ang II, losartan, and PD 123319. AT1 receptor (types AT1A and AT1B) mRNA abundance was measured by reverse transcription-polymerase chain reaction. Ang II produced concentration-dependent increases in [Ca2+]i values in atrial and ventricular cells were similar but Ang II (10-9 mol/L)-induced [Ca2+]i changes were significantly greater in atrial compared with ventricular cells Ang II responses were blocked by losartan (10-7 mol/L) but not PD 123319 (10-7 mol/L). Binding studies demonstrated a single class of high-affinity. Ang II binding sites on cardiomyocyte membranes (Kd = 0.71 +/- 0.11 mumol/L). 125I-[Sar1,Ile8]Ang II was displaced by losartan but not by PD 123319. AT1 receptor mRNA was detected by reverse transcription-polymerase chain reaction in cells from atria and ventricles. In atrial cardiomyocytes, both AT1A and AT1B receptor genes were expressed, whereas in ventricular cardiomyocytes, only the AT1A receptor gene was expressed. These data demonstrate that neonatal cardiomyocytes possess Ang II receptors of the AT1 receptor subtype that are linked to [Ca2+]i signaling pathways. The different Ang II-induced [Ca2+]i responses between atrial and ventricular cells may be related to differences in the distribution of AT1 receptor subtype subvariants.

Angiotensin II↗
PubMed1996

Intracellular Ca2+ modulation by angiotensin II and endothelin-1 in cardiomyocytes and fibroblasts from hypertrophied hearts of spontaneously hypertensive rats.

The vasoactive peptides angiotensin II (Ang II) and endothelin-1 (ET-1) have been implicated in cardiac hypertrophy. This study investigates Ang II and ET-1 effects on intracellular free calcium concentration and the receptor subtype through which agonist-induced calcium responses are mediated in isolated cardiomyocytes and fibroblasts from hypertrophied hearts of spontaneously hypertensive rats (SHR). We measured intracellular free calcium concentration by fura 2 methodology and determined receptor status by radioligand binding assays. Ang II (10(-12) to 10(-7) mol/L) had no effect on cardiomyocyte calcium levels in control Wistar-Kyoto rats but significantly increased (P < .01) intracellular free calcium concentration in a dose-dependent manner in cardiomyocytes from SHR. Ang II total and specific binding were increased (P < .05) in SHR cardiomyocytes. Calcium responses elicited by 10(-7) to 10(-5) mol/L Ang II were significantly reduced (P < .01) in SHR fibroblasts despite no significant change in Ang II receptor density. The angiotensin type 1 receptor blocker losartan (1 mumol/L) blocked Ang II-stimulated calcium transients, whereas the angiotensin type 2 receptor blocker PD 123319 had no effect. ET-1- and sarafotoxin S6c-induced calcium responses in cardiomyocytes and fibroblasts were not different between hypertensive and control groups. In conclusion, Ang II and ET-1 elicit distinct and differential responses in a cell-specific manner in cardiomyocytes and fibroblasts from hypertrophied hearts of SHR. Whereas Ang II-mediated effects, which are elicited via angiotensin type 1 receptors, are detectable in cardiomyocytes from SHR, responses to Ang II are blunted in fibroblasts from SHR, and ET-1-related actions are similar in cells from both rat groups. Stimulation of cardiomyocytes by Ang II in hypertrophied hearts associated with pressure overload in genetic hypertension suggests that Ang II could modulate the function of cardiomyocytes of SHR but not those of Wistar-Kyoto rats, whereas cardiac actions of ET-1 do not change with the development of hypertension.

Angiotensin II↗
PubMed1996

Endothelin-1 and angiotensin II receptors in cells from rat hypertrophied heart. Receptor regulation and intracellular Ca2+ modulation.

This study investigates the cellular localization and regulation of endothelin-1 (ET-1) and angiotensin II (Ang II) receptors and the effects of ET-1 and Ang II on [Ca2+]i in cardiac hypertrophy due to volume overload in the rat. Radioligand binding assays and [Ca2+]i measurements by fura 2 methodology were performed on isolated ventricular cardiomyocytes and fibroblasts from the heart of rats with a 4-week aortocaval shunt. In the hypertrophied myocardium, ET-1 and Ang II concentrations were unchanged in ventricles. Ventricular ET-1 receptors had a cell-specific distribution: > 90% of ET receptors in cardiomyocytes are of the ETA subtype, whereas fibroblasts had a nearly equal proportion of the ETA and ETB subtypes. ET-1 receptor densities, affinities, and ET-1-induced [Ca2+]i were not significantly different from control in both ventricular cell types from hypertrophied myocardium. Ang II specific binding was very low on isolated ventricular cardiomyocytes, suggesting few receptors in control conditions. However, [Ca2+]i responses induced by Ang II at concentrations > 10(-8) mol/L were detectable and were significantly higher in hypertrophied cardiomyocytes. Ang II receptor density (exclusively AT1) on fibroblasts was significantly reduced (42,970 +/- 3330 versus 73,870 +/- 7940 sites per cell for control cells, P < .01), but AT1 receptor affinity was unchanged after volume overload. The maximum increase in [Ca2+]i evoked by 10(-6) to 10(-4) mol/L Ang II was significantly lower in fibroblasts from overloaded hearts. In conclusion, ET-1 receptor proportion is cell specific, with cardiomyocytes possessing predominantly the ETA subtype and fibroblasts possessing both ETA and ETB receptors. Plasma and cardiac ET-1 concentrations and ET-1 receptor regulation on both ventricular cell types are not altered in cardiac volume overload, suggesting that cardiac ET-1 may not play a significant role in this model. Cardiac hypertrophy induced a significant downregulation of AT1 receptors on fibroblasts, whereas total binding and [Ca2+]i sensitivity to Ang II were significantly enhanced in hypertrophied cardiomyocytes. This suggests that cardiac Ang II may be involved in the pathophysiology of the cardiac hypertrophy of volume overload.

Angiotensin II↗
PubMed1995

Molecular analysis of human prorenin prosegment variants in vitro and in vivo.

The aspartyl protease renin, an important modulator of blood pressure in humans, is present in the circulation not only in its active form, but also as an inactive precursor, prorenin, in which a 43-amino acid prosegment blocks access of the substrate to the active site of the enzyme. Site-directed mutagenesis of the prosegment has led to the following conclusions. 1) Maintenance of the enzymatically inactive state of prorenin requires a short peptide sequence between positions 10P and 20P (where P denotes prosegment and numbering is relative to amino terminus) of the prosegment; and 2) there is an inverse relationship between the ability of prosegment mutations to activate and their effect on the secretion of the various prorenins, suggesting that this same region of the prosegment plays a critical role in the biosynthesis of human prorenin. Since these results demonstrated that single amino acid mutations could activate human prorenin to varying degrees, mutations in this region of the renin gene could be clinically important in humans. To test this hypothesis, genomic screening was carried out on the corresponding region of the human renin gene (exon 2) in a cohort of patients selected for a likely familial component to their hypertension. While this study identified a novel polymorphism in exon 2 of the human renin gene, evidence was not obtained for either the presence of prosegment mutations or the association of the novel polymorphism with hypertension in the patient population studied. In conclusion, both structure-function studies and genetic screening suggest that mutation of the prorenin prosegment is an unlikely factor in activation of the renin-angiotensin system in humans.

Amino Acid Sequence↗
PubMed1995

Compared TCR and CD3 epsilon expression on alpha beta and gamma delta T cells. Evidence for the association of two TCR heterodimers with three CD3 epsilon chains in the TCR/CD3 complex.

Current models for TCR/CD3 complex stoichiometry involve one or alternatively two TCR heterodimer(s) associated with two CD3 epsilon per complex. They mainly constructed on the basis of biochemical studies involving disruption of membrane complexes. The present study was undertaken to quantify the relative proportions of CD3 epsilon and TCR chains on alpha beta and gamma delta lymphocytes in nondenaturing conditions. Quantitative flow cytometry revealed that alpha beta and gamma delta PBL express on an average 1.56 and 1.52 more CD3 epsilon-chain than beta- and delta-chains, respectively. Accordingly, CD3 epsilon to TCR-alpha, TCR-beta, TCR-gamma, and TCR-delta ratios found on three polyclonal cell lines and on Jurkat cells were all very close to 1.50. These results clearly demonstrate that alpha beta as well as gamma delta T cells express approximately 1.50 more CD3 epsilon-chain than each of the TCR chains. They strongly suggest that alpha beta and gamma delta TCR/CD3 complexes involve two TCR heterodimers associated with three CD3 epsilon-chains (or a multiple of this combination). In addition, our results showed that gamma delta PBL expressed about 1.90 more TCR (-delta vs -beta) and CD3 epsilon-chains than alpha beta PBL. Furthermore, TCR-beta expression and CD3 epsilon expression were higher on CD4+ alpha beta PBL than on CD8+ alpha beta PBL, whereas TCR-delta expression and CD3 epsilon expression were both identical on CD8+ gamma delta PBL and on CD8- gamma delta PBL. These results demonstrate that CD8+ or CD8- gamma delta PBL, CD4+ alpha beta PBL and CD8+ alpha beta PBL express decreasing levels of the TCR/CD3 complex.

CD3 Complex↗
PubMed1995

Evidence of noninvolvement of swine MHC class II in the in vitro proliferative response of human lymphocytes to porcine endothelial cells.

Successful pig-to-human xenotransplantation may expose swine endothelium to the human immune system. Since endothelial MHC class II expression is crucial in the genesis of an allogeneic lymphocyte response, the involvement of porcine MHC (SLA) class II molecules in the induction of human lymphocyte proliferation was studied. When cocultured with a confluent monolayer of irradiated porcine aortic endothelial cells (PAEC), human peripheral blood mononuclear cells (PBMC) incorporated tritiated thymidine. Monocyte depletion strongly reduced the magnitude of the lymphocyte proliferative response. Resting cultured PAEC were SLA class II-negative and an induction of these molecules during the xenogeneic mixed lymphocyte endothelial cell culture (XMLEC) was not observed. Moreover, the addition of an antibody directed against the SLA-DR molecule was without effect. Lymphocyte proliferation was also studied in response to SLA class II-positive stimulating cells--either human TNF-alpha-stimulated PAEC or porcine splenocytes. Induction of SLA class II molecules on PAEC had no effect on the human PBMC proliferative response. Moreover, human PBMC did not proliferate in response to porcine splenocytes. These results suggest (1) that SLA class II molecules are not involved in the induction of the human lymphocyte proliferative response and (2) that the endothelial nature of the stimulating cells plays a key role in this proliferation.

Animals↗
PubMed1995

Increased endothelin-1 gene expression in the endothelium of coronary arteries and endocardium in the DOCA-salt hypertensive rat.

Endothelin-1 (ET-1) is a potent vasoconstrictor and inotropic agent which may also induce cell hypertrophy. The role of ET-1 in ventricular hypertrophy in hypertension is unknown. We investigated ET-1 gene expression and immunoreactive ET-1 (ir-ET-1) concentration in the heart of deoxycorticosterone acetate (DOCA)-salt hypertensive rats. To identify the cellular sites of ET-1 production in the heart, we performed in situ hybridization histochemistry. DOCA-treated rats which underwent unilateral nephrectomy (Uni-Nx) or not, exhibited mild systolic blood pressure elevation and ventricular hypertrophy. Blood pressure elevation and cardiac hypertrophy were more severe in DOCA-salt hypertensive rats. Ventricular ET-1 mRNA was similar in Uni-Nx control and DOCA-treated rats by Northern blot analysis, whereas in DOCA-salt hypertensive rats it was significantly increased. Ir-ET-1 concentration was also enhanced in ventricles from DOCA-salt hypertensive rats compared with Uni-Nx control rats. In situ hybridization histochemistry using a 35S-labelled complementary RNA ET-1 probe demonstrated that the level of ET-1 mRNA transcripts was increased exclusively in endothelial cells of large epicardial and small intramyocardial coronary arteries and in areas of the endocardium, but not significantly in myocardial cells of either the atria or ventricles. Enhanced ET-1 production may contribute to vascular changes, both structural and functional, in the heart in this model of hypertension in the rat, but probably does not contribute to the severe cardiac hypertrophy found in DOCA-salt hypertensive rats.

Animals↗
PubMed1995

Cardiac endothelin-1 content and receptor subtype in spontaneously hypertensive rats.

Endothelin-1 (ET-1), a newly discovered peptide with potent vasoconstrictor and growth-promoting effects, has been implicated in high blood pressure and cardiac hypertrophy in the spontaneously hypertensive rat (SHR). In the present study, we measured plasma ET-1 levels and tissue ET-1 concentrations in the four cardiac chambers of 17- to 18-week-old SHR and their normotensive controls. Wistar Kyoto (WKY) rats. SHR had slightly but significantly higher plasma ET-1 levels than WKY. The ventricles had the highest ET-1 content and the atria in both strains had the highest ET-1 concentrations. ET receptor subtypes were analysed by radiogand binding with ET-1, BQ-123 and IRL 1620 in crude membrane preparations of the four cardiac chambers. No differences in receptor subtype densities or affinities were apparent between the two strains. ET(A) represented 75 to 85% of both ET receptors. Competition analysis revealed that in both strains left ventricular tissue had lower receptor densities and higher affinities than the atria. These results suggest that ET-1 and its receptor although contributing in the maintenance of high blood pressure may not be an important factor during stable cardiac hypertrophy in adult SHR. The differential distribution of ET-1 content and receptor densities favoring the atria in both strains suggest that this peptide may have a different physiological role in the atria from that in the ventricles.

Animals↗
PubMed1995

Inhibition of induced lymphocyte proliferation by lipid and protein components of the syncytiotrophoblast plasma membrane.

PROBLEM: The aim of this work was to define the respective responsibilities of the lipid and protein components of syncytiotrophoblast plasma membranes on the inhibition of lymphocyte proliferation induced in vitro. METHOD: A fractionation method using octyl-beta-D-glucopyranoside enabled lipoprotein, lipid, and protein fractions to be isolated from the membrane. RESULTS: The lipid fraction was shown nonspecifically to inhibit lymphocyte proliferation, to a lower extent compared with the native membrane. Alternatively, the protein fraction used as a proteoliposome contained the totality of the cytostatic effect of the native fraction. CONCLUSION: These results are discussed generally in the context of the immunoregulatory role of membrane lipids and proteins and in relation to the local properties of syncytiotrophoblast plasma membrane components in fetal graft tolerance.

Cell Membrane↗
PubMed1995

Endothelin-1 expression in blood vessels of DOCA-salt hypertensive rats treated with the combined ETA/ETB endothelin receptor antagonist bosentan.

In previous studies it has been shown that blood vessels of deoxycorticosterone acetate (DOCA) salt hypertensive rats present significantly higher immunoreactive ET-1 (ir-ET-1) content and increased ET-1 gene expression. DOCA-salt hypertensive rats respond to treatment with the combined ETA/ETB endothelin receptor antagonist bosentan with lowering of blood pressure. In the present study, we investigated the ir-ET-1 levels and the expression of the ET-1 gene in blood vessels of DOCA-salt hypertensive rats treated or not treated with bosentan. Blood pressure was significantly lower in bosentan-treated rats (185 +/- 6 mmHg; 1 mmHg = 133.3 Pa) compared with DOCA-salt hypertensive rats (203 +/- 4 mmHg; p < 0.01). Plasma ir-ET-1 concentration was slightly but significantly elevated (p < 0.01) in DOCA-salt hypertensive rats compared with uninephrectomized control rats, and was further increased (p < 0.01) in bosentan-treated rats. The tissue wet weight and ir-ET-1 content of segments of thoracic aorta were significantly increased (p < 0.01) in DOCA-salt hypertensive rats in comparison with control rats, but were similar in bosentan-treated DOCA-salt rats. The abundance of ET-1 mRNA measured by Northern blot analysis in thoracic aorta and the ir-ET-1 content were attenuated by bosentan treatment. Tissue wet weight and ir-ET-1 content in the mesenteric vascular bed were similar in bosentan-treated and -untreated DOCA-salt rats, and were significantly higher in both groups than in control rats (p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗