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T J Resink

Publications and source records attributed to T J Resink.

At least 73 records · Page 4Linked to original sources
PubMed1989

Epidermal growth factor responsiveness in smooth muscle cells from hypertensive and normotensive rats.

Aortic smooth muscle cells from spontaneously hypertensive rats (SHR) exhibit inappropriate proliferation characteristics in culture that suggest a modified response to serum mitogens or growth factors. The present study compares vascular smooth muscle cells from SHR and normotensive Wistar-Kyoto (WKY) rats with respect to their proliferative and functional response to growth factors. Specific attention was focused on the interaction of these vascular smooth muscle cells with epidermal growth factor. An increased growth rate of vascular smooth muscle cells from SHR (vs. WKY rats) was observed when cells were cultured in the presence of serum (10% and 0.5%), but not under serum-free conditions. The additional presence of low serum concentrations (0.5%) was required for epidermal growth factor to elicit a proliferative response, whereupon smooth muscle cells from SHR displayed an increased (vs. WKY rats) growth rate. Saturation binding of [125I]epidermal growth factor to intact smooth muscle cells indicated a twofold increase in receptor density in SHR-derived cells (p less than 0.001 vs. WKY rats) without an alteration in affinity for the growth factor. Cells derived from SHR also exhibited greater functional responsiveness to epidermal growth factor when compared with smooth muscle cells from WKY rats as evidenced by amplifications of both S6 kinase activation, phosphoinositide catabolism, elevation of intracellular pH, and DNA synthesis (nuclear labeling). We conclude that increased responsiveness of SHR-derived smooth muscle cells to epidermal growth factor could contribute to alterations in vascular smooth muscle growth and tone that may be fundamental to the pathogenesis of hypertension and atherosclerosis.

Animals↗
PubMed1989

Enhanced responsiveness to angiotensin II in vascular smooth muscle cells from spontaneously hypertensive rats is not associated with alterations in protein kinase C.

This study compares vascular smooth muscle cells from spontaneously hypertensive and normotensive Wistar-Kyoto rats with respect to protein kinase C and intracellular responses to angiotensin II (Ang II). Ang II-induced degradation of polyphosphoinositides and accumulation of inositol di- and tris-phosphates was enhanced (approximately twofold) in hypertensive-derived cells, without a change (vs. normotensive-derived cells) in half-maximally effective concentrations of Ang II. Intracellular pH (approximately 6.6) was comparable between both cell isolates at quiescence, but alkalinization induced by Ang II, serum, or phorbol ester was greater (delta 0.1-0.2 pH units) for hypertensive-derived cells. For both cell types, the intracellular pH response to these agonists was prevented in the presence of Na+-H+ exchange inhibitors. S6 kinase activation induced by Ang II was enhanced (approximately twofold) in hypertensive-derived cells, whereas activation in response to serum or 12-O-tetradecanoylphorbol 13-acetate did not differ significantly between the two cell types. Quantitation of protein kinase C by immunoblotting and [3H]phorbol dibutyrate binding procedures revealed no differences between the two smooth muscle cell isolates (at quiescence or in the presence of serum) with respect to either total amounts or subcellular distribution. Sensitivity of protein kinase C to phorbol ester was apparently also not different between the two cell types, as assessed from dose-dependent (phorbol ester) S6 kinase activation profiles. Phorbol ester caused a similar subcellular redistribution of [3H]phorbol dibutyrate binding in the two cell isolates, but for both, minimal (10%) translocation occurred in response to Ang II. The data suggest that enhanced agonist responsiveness in vascular smooth muscle cells is unlikely to involve alterations in protein kinase C.

Angiotensin II↗
PubMed1989

The vasodilating effect of atrial natriuretic peptide in normotensive and hypertensive humans.

Atrial natriuretic peptide (ANP) infused intra-arterially into the forearm results in a dose-dependent vasodilator response of rapid onset. The maximal forearm vasodilator response to ANP amounts to about 60% of the maximal forearm vasodilator response to sodium nitroprusside and combined infusion of ANP and sodium nitroprusside has an additive vasodilator effect. ANP-induced vasodilation is greater than that of postjunctional alpha 1- or alpha 2-adrenoceptor blockade or of beta 2-adrenoceptor stimulation but is smaller than due to calcium entry blockade. ANP-induced vasodilation can easily be overcome by norepinephrine and to a lesser extent by angiotension II (Ang II). The similarity of the dose-response relationships for vasodilation and for natriuresis suggests that ANP may be equally effective on its renal and vascular targets. In patients with essential hypertension, intra-arterial infusion of ANP produced a greater vasodilator response than in normotensives and this was inversely related to plasma renin activity, suggesting greater vasodilator responsiveness to ANP in low-renin hypertension. ANP caused vasodilation in humans but this may become less apparent when ANP is infused into the systemic circulation because of cardiovascular sympathetic reflex mechanisms blunting ANP vasodilation. Although the role of ANP in circulatory disease states is unclear, it appears that it could serve a physiological function as an endogenous vasodilator (and natriuretic) principle for volume homeostasis in humans.

Atrial Natriuretic Factor↗
PubMed1989

Enhanced growth and growth factor responsiveness of vascular smooth muscle cells from hypertensive rats.

Vascular smooth muscle cells from spontaneously hypertensive rats (SHR) exhibited enhanced growth rates in culture when compared to cells from their normotensive, Wistar-Kyoto (WKY) counterparts. Proliferation rates were dependent on supplementation levels of fetal calf serum (FCS) in culture medium and the passage number of the cells studied. Cells from hypertensive animals were more responsive to a number of agonists, as assessed by activation of S6 kinase and elevation of intracellular pH than those derived from WKY animals. Furthermore, SHR-derived cells exhibited enhanced turnover of phosphoinositides when exposed to epidermal growth factor or angiotensin II as compared to cells from normotensive rats treated in the same way. The latter cells were, however, more susceptible to growth inhibition by heparin than their hypertensive counterparts and possessed twice the number of specific cell surface heparin receptors as SHR-derived cells. Both cell types showed a marked stimulation of proliferation rates when they were cultured on extracellular matrix coated plasticware. Matrices elaborated by SHR-derived cells were more stimulatory to growth than those derived from WKY sources.

Animals↗
PubMed1988

Endothelin stimulates phospholipase C in cultured vascular smooth muscle cells.

Cultured vascular smooth muscle cells from bovine and rat thoracic aortae and from human omental vessels have been examined for cellular responses to endothelin. In myo-[3H]-inositol-prelabelled cells endothelin induced a rapid (within 30 sec) and protracted increase of [3H]-inositol content in inositol bis- and tris-phosphates. Concomitantly, significant polyphosphoinositide hydrolysis occurred within 30 sec. Accumulation of [3H]-inositol monophosphate and hydrolysis of phosphatidylinositol were delayed. In cells prelabelled with [3H]-arachidonic acid endothelin promoted rapid production of [3H]-diacylglycerol which decayed slowly toward control values after reaching maximum levels (1-2 min). Half-maximally effective concentrations of endothelin for all these cellular responses were comparable (approximately 3-7 nM) and not significantly different between the vascular cell isolates. The involvement of the phospholipase C-signal transduction pathway in mediating endothelin-induced vasoconstriction is invoked.

Animals↗
PubMed1988

Involvement of Ni protein in the functional coupling of the atrial natriuretic factor (ANF) receptor to adenylate cyclase in rat lung plasma membranes.

In the presence of 1 microM atrial natriuretic factor (ANF) and low (0.1 mM) Mg2+ concentrations, the initial rate of binding of [3H]guanosine 5'-[beta, gamma-imido)triphosphate [( 3H]p[NH]ppG) to rat lung plasma membranes was increased twofold to threefold. ANF-dependent stimulation of the initial rate of [3H]p[NH]ppG binding was reduced at high (5 mM) Mg2+ concentrations. Preincubation of membranes with p[NH]ppG (5 min at 37 degrees C) eliminated the ANF-dependent effect on [3H]p[NH]ppG binding whereas ANF-dependent [3H]p[NH]ppG binding was unaffected by similar pretreatment with guanosine 5'-[beta-thio]diphosphate (GDP[beta S]). An increase in ANF concentration from 10 pM to 1 microM caused a 40% decrease in forskolin-stimulated or isoproterenol-stimulated adenylate cyclase activities (IC50 5 nM) in rat lung plasma membranes. GTP (100 microM) was obligatory for the ANF-dependent inhibition of adenylate cyclase, which could be completely overcome by the presence of 100 microM GDP[beta S] or the addition of 10 mM Mn2+. Reduction of Na2+ concentration from 120 mM to 20 mM had the same effect. Pertussis toxin eliminated ANF-dependent inhibition of adenylate cyclase by catalyzing ADP-ribosylation of membrane-bound Ni protein (41-kDa alpha subunit of the inhibitory guanyl-nucleotide-binding protein of adenylate cyclase). The data support the notion that one of the ANF receptors in rat lung plasma membranes is negatively coupled to a hormone-sensitive adenylate cyclase complex via the GTP-binding Ni protein.

Adenosine Diphosphate Ribose↗
PubMed1988

Atrial natriuretic peptide induces breakdown of phosphatidylinositol phosphates in cultured vascular smooth-muscle cells.

Discrepancies exist between extent of guanylate cyclase activation by atrial natriuretic peptide (ANP) in cell-free systems and ANP-stimulated levels of cyclic GMP in whole cells, and also between receptor affinity and dose effectiveness of ANP. Therefore, we have investigated whether, in addition to receptor-coupled guanylate cyclase activation, other second-messenger cascade systems may be involved in mediating both an increase in cyclic GMP and the physiological response to ANP. Equilibrium 125I-ANP binding studies on cultured thoracic aorta smooth muscle cells revealed the existence of low-affinity (approximately 10(-8) M, 84.5 fmol/10(5) cells) and high-affinity (approximately 10(-10) M, 12.5 fmol/10(5) cells) binding sites. We confirm that ANP elevates intracellular cyclic GMP (EC50 approximately 10(-8) M) and inhibits agonist-(isoproterenol and forskolin)-induced increases in intracellular cyclic AMP (IC50 approximately 10(-9) M). ANP also stimulated breakdown of phosphatidylinositol phosphates and generation of inositol phosphates with a half-maximally effective concentration of approximately 10(-10) M. The extent of phosphatidylinositol polyphosphate hydrolysis was small (120%) in comparison to that of phosphatidylinositol (Ptd-Ins) (200%). Ptd-Ins hydrolysis was paralleled by the appearance of glycerophosphoinositol, and there was also a close temporal relationship between these processes and the accumulation of intracellular cyclic GMP. Smooth muscle cells released [3H]arachidonic acid label in response to ANP (EC50 approximately 10(-10) M). Taken together, the data suggest that the vasorelaxant hormone ANP has stimulatory effects on phosphoinositol lipid metabolism via both phospholipase C (generation of inositol phosphates) and phospholipase A2 (generation of releasable [3H]arachidonic acid and indirectly glycerophosphoinositol). In contrast, stimulation of phosphatidylinositol phosphate breakdown by the vasoconstrictive hormone angiotensin II is not associated with glycerophosphoinositol formation, and neither cyclic GMP nor cyclic AMP levels were influenced by this hormone.

Angiotensin II↗
PubMed1988

Amiloride sensitive activation of S6 kinase by angiotensin II in cultured vascular smooth muscle cells.

Angiotensin II was shown to activate S6-kinase in cultured vascular smooth muscle cells (VSMC) in a dose- (10(-9)-10(-6) M) and time-dependent manner. Pretreatment of quiescent cells with 12-O-Tetradecanoylphorbol-13-acetate had no effect on the activation levels of the kinase at the hormone levels used. However, stimulation of S6-kinase activity by angiotensin II was markedly inhibited by the inclusion of amiloride hydrochloride in serum-free medium during activation procedures. Angiotensin was not mitogenic for VSMC at even the highest doses used (10(-6) M). These findings support the notion that raised intracellular pH results in the activation of protein synthesis in quiescent cells.

Amiloride↗
PubMed1988

Platelet abnormalities and the pathophysiology of essential hypertension.

The mechanisms whereby intracellular calcium concentration is controlled are briefly reviewed. With the current knowledge of both calcium homeostasis and the function and properties of cellular Ca2+-target proteins/signal transduction systems, a dysfunction of cellular calcium metabolism is considered in relation to the pathogenesis of hypertension. Although the enhanced peripheral vascular resistance characteristic of hypertension is ultimately a function of Ca2+ availability for smooth muscle cell contraction, the platelet possesses many parallel biochemical and physiological properties. Therefore, we have utilized the platelet as the cell-model for investigating the role of Ca2+ in hypertension disorders. An overview of Ca2+-linked platelet processes altered in essential hypertension is presented, and an attempt is made to integrate these multiple aberrations in a fundamental membrane lesion.

Blood Platelets↗
PubMed1988

Activation of S6 kinase in cultured vascular smooth muscle cells by submitogenic levels of thrombospondin.

Purified human platelet thrombospondin was shown to activate S6 kinase in cultured vascular smooth muscle cells in a dose- (1-9 micrograms/ml) and time-dependent manner. Down regulation of epidermal growth factor and somatomedin C receptors by prior treatment of cells with their respective growth factors did not reduce this effect. Kinase activation by thrombospondin was only marginally reduced in the presence of platelet-derived growth factor specific antibody at levels that totally inhibited platelet-derived growth factor (5 ng/ml) induced activation. Additionally, thrombospondin elicits a rapid dose-dependent phosphoinositide turnover response analogous to that of platelet-derived growth factor, epidermal growth factor and somatomedin C. Prior treatment of cells with phorbol ester for 48 hrs in serum-free culture medium resulted in a small enhancement of S6 kinase activation by thrombospondin and the above mentioned growth factors but a complete loss in the ability of phorbol ester to activate this enzyme. These findings with cultured smooth muscle cells suggest a growth factor-like role for thrombospondin.

Animals↗
PubMed1988

Platelet membrane and calcium control abnormalities in essential hypertension.

The mechanisms whereby intracellular calcium concentration is controlled are briefly reviewed. With the current knowledge of both calcium homeostasis and the function and properties of cellular Ca2+-target proteins/signal transduction systems, a dysfunction of cellular calcium metabolism is considered in relation to the pathogenesis of hypertension. Although the enhanced peripheral vascular resistance characteristic of hypertension is ultimately a function of Ca2+ availability for smooth muscle cell contraction, the platelet possesses many parallel biochemical and physiologic properties. Therefore, we have utilized the platelet as the cell model for investigating the role of Ca2+ in hypertension disorders. An overview of Ca2+-linked platelet processes altered in essential hypertension is presented, and an attempt is made to integrate these multiple aberrations in a fundamental membrane lesion.

Adenylyl Cyclases↗
PubMed1988

Growth regulation in smooth muscle cells from normal and hypertensive rats.

Smooth muscle cell proliferation is regulated through the coordinated interaction of growth factors/mitogens and growth inhibitors such as heparin. Vascular smooth muscle cells isolated from the thoracic aorta of adult male spontaneously hypertensive rats (SHR) proliferated faster and reached higher cell densities during 8-day culture periods than cells isolated from age- and sex-matched Wistar-Kyoto (WKY) animals. Since both cell isolates were exposed to the same array of growth factors present in fetal calf serum, the differences in proliferation rates were indicative of a differential responsiveness between the two cell types to such factors. Cultures from SHR and WKY rendered quiescent by serum withdrawal were shown to respond to epidermal growth factor in a differential manner, whereas they exhibited similar responsiveness to platelet-derived growth factor and somatomedin C. Cells from hypertensive animals expressed twice as many specific cell surface receptors for epidermal growth factor as their normotensive counterparts. However, in contrast the latter possessed double the number of specific cell surface heparin binding sites when compared to cells from hypertensive animals. The coordinated interaction of heparin epidermal growth factor and extracellular matrix thrombospondin may be a mechanism for vascular smooth muscle growth regulation.

Animals↗
PubMed1987

Dependence of urokinase-type-plasminogen-activator induction on cyclic AMP-dependent protein kinase activation in LLC-PK1 cells.

The activation of cyclic AMP-dependent protein kinase (cAMP-PK) in vivo was studied in LLC-PK1 pig kidney cells and the mutant cell lines M18 and FIB5, which have total levels of cAMP-PK catalytic-subunit and regulatory-subunit activities comparable with those of parental cells. The extent of cAMP-PK activation (release of active catalytic subunit from the holoenzyme) was directly correlated with the cellular cyclic AMP concentration in LLC-PK1 cells. In LLC-PK1 cells, as well as in the mutants M18 and FIB5, the extent of the induction of urokinase-type plasminogen activator (uPA) by the cyclic AMP-mediated effectors calcitonin, vasopressin and forskolin was directly correlated with the levels of activated catalytic subunit. The 'receptorless' mutant M18, which is impaired in calcitonin- and vasopressin-receptor function, did not show any activation of cAMP-PK or uPA production in response to either hormone, whereas cAMP-PK and uPA responses to forskolin were about 35% higher than in parental cells. Analysis of the FIB5-cell line revealed a lesion affecting the regulation of adenylate cyclase activity, whereby basal and stimulated (both receptor- and non-receptor-mediated) adenylate cyclase levels were less than 36% of those in parental cells. The activation of cAMP-PK in response to cyclic AMP effectors was similarly reduced, and uPA induction was concomitantly lower than that in parental cells. The results demonstrate the dependence of uPA induction by cyclic AMP effectors on dissociation of the cAMP-PK holoenzyme, implying the importance of activated free cAMP-PK catalytic subunit in this process. Thus it is concluded that the mutations in the cellular cyclic AMP-generating apparatus of the M18 and FIB5 cell lines impair uPA induction by preventing cAMP-PK activation.

Adenylyl Cyclases↗
PubMed1987

Histamine-induced phosphoinositide metabolism in cultured human umbilical vein endothelial cells. Association with thromboxane and prostacyclin release.

Histamine stimulation of cultured human umbilical vein endothelial cells induced dose- and time-dependent increases in glycerophosphoinositol (GroPIns), inositol-1-phosphate (InsP), inositolbisphosphate (InsP2) and inositoltrisphosphate (InsP3) in addition to release of thromboxane A2 and prostacyclin. Increases in InsP2 and InsP3 were immediate while increases in GroPIns and InsP occurred only after 1 min. Thromboxane A2 and prostacyclin release paralleled GroPIns and InsP production. The data indicate that, in endothelial cells, histamine evokes early hydrolysis of polyphosphoinositides, and that subsequent mobilization of arachidonic acid for thromboxane and prostacyclin synthesis involves both deacylation and phosphodiesteratic cleavage of phosphatidylinositol.

6-Ketoprostaglandin F1 alpha↗
PubMed1987

Complementation between LLC-PK1 mutants affected in polypeptide hormone-receptor function.

The mutant LLC-PK1 cell lines FIB6 and FIB5/N4 were examined for responsiveness to the polypeptide hormones calcitonin and vasopressin. Both mutants exhibited little or no activation of adenylate cyclase or cAMP-dependent protein kinase (cAMP-PK) in response to calcitonin, but responded to vasopressin. Analysis of calcitonin receptor function demonstrated that both mutants bound less than 9 fmol 125I-labeled salmon calcitonin/mg cellular protein, which was about 1% of parental activity (642 fmol calcitonin bound/mg). Concomitant with reduced calcitonin binding, both mutants exhibited increased vasopressin binding (greater than 272 fmol [[3H]Arg]vasopressin bound/mg) compared to parental (166 fmol bound/mg). The concentration of vasopressin for half-maximal stimulation of adenylate cyclase in both mutants was comparable to that for LLC-PK1 cells (40 pM) and hence the increased binding activity was concluded to be due to increased numbers of functional vasopressin receptors in the mutants. Somatic cell hybrids formed between each mutant and LLC-PK1 cells exhibited normal hormone binding and activation of cAMP-PK in response to both vasopressin and calcitonin. The mutations affecting receptor function in FIB6 and FIB5/N4 were accordingly concluded to be recessive. Somatic cell hybrids between FIB6 and FIB5/N4 showed no complementation of the mutant phenotype, indicating that both cell lines were affected in the same gene. In contrast, somatic cell hybrids between FIB5/N4 and the 'receptorless' mutant M18 (which lacks functional calcitonin and vasopressin receptors) exhibited approximately the same responsiveness to vasopressin and to calcitonin as LLC-PK1. Complementation between two different mutations affecting polypeptide receptor function was thus observed. The results are discussed in terms of a proposed common pathway for processing of calcitonin and vasopressin receptors.

Adenylyl Cyclases↗
PubMed1987

The vasodilator potency of atrial natriuretic peptide in man.

The vasodilating potency of alpha-human atrial natriuretic peptide (alpha-hANP) was investigated in the forearms of 16 normotensive subjects, 22 to 48 (mean 28) years old, with the use of venous occlusion plethysmography. alpha-hANP, 0.005 to 1.5 micrograms/min/100 ml forearm volume (FAV), infused in nine dose steps into the brachial artery increased forearm blood flow (FAF; ml/min/100 ml FAV) from 2.8 +/- 0.4 (SEM) to a maximum of 9.6 +/- 1.1. Forearm vascular resistance (mean arterial pressure/FAF) decreased by 72%. The alpha-hANP dose that produced a 50% vasodilator response was 0.093 +/- 0.016 microgram/min/100 ml FAV (n = 11) and it resulted in a venous plasma concentration of ANP (pANP) of 115 +/- 7 pmol/liter (normal 2 to 80; radioreceptor assay). Intraindividually, the maximum dose of alpha-hANP induced an increase in FAF that was 60% of the maximum response to sodium nitroprusside (14.1 +/- 1.8). Combined infusions (n = 9) of maximum forearm vasodilator doses of alpha-hANP and nitroprusside increased FAF to 22.7 +/- 3.4; this additive vasodilator effect of alpha-hANP and nitroprusside is consistent with their different actions on the guanylate cyclase system. In man, the direct vasorelaxant effect of alpha-hANP occurs at concentrations within the upper normal range of pANP, suggesting a physiologic vasodilator role for alpha-hANP.

Adult↗