Biomedical subjects

O Traub

Publications and source records attributed to O Traub.

At least 73 records · Page 4Linked to original sources

PubMed1994

Immunochemical characterization of the gap junction protein connexin45 in mouse kidney and transfected human HeLa cells.

Antibodies to the gap junction protein connexin45 (Cx45) were obtained by immunizing rabbits with fusion protein consisting of glutathione S-transferase and 138 carboxy-terminal amino acids of mouse Cx45. As shown by immunoblotting and immunofluorescence, the affinity-purified antibodies recognized Cx45 protein in transfected human HeLa cells as well as in the kidney-derived human and hamster cell lines 293 and BHK21, respectively. In Cx45-transfected HeLa cells, this protein is phosphorylated as demonstrated by immunoprecipitation after metabolic labeling. The phosphate label could be removed by treatment with alkaline phosphatase. A weak phosphorylation of Cx45 protein was also detected in the cell lines 293 and BHK21. Treatment with dibutyryl cyclic adenosine- or guanosine monophosphate (cAMP, cGMP) did not alter the level of Cx45 phosphorylation, in either Cx45 transfectants or in 293 or BHK21 cells. The addition of the tumor-promoting agent phorbol 12-myristate 13-acetate (TPA) led to an increased 32P phosphate incorporation into the Cx45 protein in transfected cells. The Cx45 protein was found in homogenates of embryonic brain, kidney, and skin, as well as of adult lung. In kidney of four-day-old mice, Cx45 was detected in glomeruli and distal tubules, whereas connexin32 and -26 were coexpressed in proximal tubules. No connexin43 protein was detected in proximal tubules. No connexin43 protein was detected in renal tubules and glomeruli at this stage of development. Our results suggest that cells in proximal and distal tubules are interconnected by gap junction channels made of different connexin proteins. The Cx45 antibodies characterized in this paper should be useful for investigations of Cx45 in renal gap junctional communication.

Animals↗

PubMed1994

Alteration in expression of gap junction proteins in rat liver after treatment with the tumour promoter 3,4,5,3',4'-pentachlorobiphenyl.

Polychlorinated biphenyls (PCBs) are industrial chemicals which are highly persistent and widely distributed in the environment. We have previously shown that 3,4,5,3',4'-pentachlorobiphenyl (PCB 126) is a potent tumour promoter in two separate 20 week initiation-promotion studies. In the present study, rat livers from these two studies were further investigated for connexin expression. The results demonstrated that treatment with PCB 126 caused a decrease in the amount of the two major liver connexins, cx 26 and cx 32, in livers of treated animals. This reduction was also prominent after treatment at low doses, although gamma-glutamyl transpeptidase-positive foci had not developed in these livers. The quantity of cx 26 and cx 32 in immunostained liver sections was determined using a computerized fluorescence image analyzer. Western blot analysis of liver extracts confirmed these results. No changes in the RNA levels in the treated rats were seen, suggesting that the down-regulation of cx 26 and cx 32 is post-transcriptional.

Animals↗

PubMed1994

Regulation of connexin26 and connexin43 expression in rat endometrium by ovarian steroid hormones.

A distinct spatial and temporal pattern of connexin26 and connexin43 (cx26 and cx43) expression was observed in the rat endometrium in response to embryo implantation; however, connexin expression was suppressed during the preimplantation period. Pseudopregnant rats did not show connexin mRNA, while artificial decidualization induced by a scratch led to a strong expression of cx26 and cx43 in the endometrium of these animals. In order to examine the regulatory effects of ovarian steroid hormones on connexin expression, ovariectomized rats were treated with progesterone (P) and/or estradiol-17 beta (E2). Untreated, ovariectomized animals expressed mRNA for cx43, but not for cx26. Endometrial expression of mRNA for both connexins was strongly enhanced by E2 treatment; immunolabeling revealed protein for cx26 in the uterine luminal epithelial cells and for cx43 in the uterine stromal cells. P treatment, either alone or in combination with E2, suppressed expression of connexin mRNA. P suppression in the presence of E2 was reversible when P was withdrawn. When administered on Days 0-2 of pregnancy, the antiprogestin onapristone inhibited the effect of P and gave rise to strong expression of both connexin transcripts. These results demonstrate that expression of cx26 and cx43 in the rat uterine endometrium is differentially regulated by E2 and P during early pregnancy.

Animals↗

PubMed1994

Effects of ramipril on contractile oscillations in arteries from genetically hypertensive rats.

We have tested the hypothesis that altered vascular reactivity, specifically the appearance of spontaneous and BayK 8644 (L-type voltage gated calcium channel agonist)-induced oscillations in the carotid artery and the sarcoplasmic reticulum Ca(2+)-ATPase inhibitor cyclopiazonic acid (CPA)-induced oscillations in the aorta from stroke-prone spontaneously hypertensive rats (SHRS), are dependent upon angiotensin II production early in life. SHRSP and normotensive Wistar-Kyoto (WKY) rats were treated from 6-10 weeks of age with vehicle, hydralazine/hydrochlorothiazide (used as a control for lowered blood pressure) or the angiotensin converting enzyme inhibitor ramipril (3 mg/kg/day). Systolic blood pressures were measured weekly in rats from 6 to 17 weeks of age. In SHRSP (at 17 weeks of age), ramipril-treatment but not hydralazine/hydrochlorothiazide attenuated the long term expression of elevated systolic blood pressure in adult SHRSP while blood pressures of all adult WKY rats were unaffected by any treatment. At 17 weeks, rats were killed and arteries removed for in vitro measurement of isometric contractile activity. Only the incidence of spontaneous oscillations (carotid artery) was affected by ramipril treatment; ramipril did not change the frequency of BayK 8644-induced oscillations in the artery or the frequency of CPA-induced oscillations in aorta from either SHRSP or WKY. These data indicate that while spontaneous oscillations in the carotid artery may be dependent on an angiotensin II-sensitive mechanism during development, agonist-induced oscillations (CPA and BayK 8644) appear not to be angiotensin II-dependent. Thus, not all of the contractile oscillations which appear in vascular smooth muscle from SHRSP are angiotensin II-dependent, suggesting that some of these vascular abnormalities may develop at a time separate from that in which increased blood pressure is firmly established and may not be associated with the for maintenance of elevated blood pressure.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗

PubMed1994

Differential expression of the gap junction proteins connexin45, -43, -40, -31, and -26 in mouse skin.

The expression of five different members of the gap junction multigene family, connexin (Cx)45, -43, -40, -31, and -26 was investigated in embryonic and adult mouse skin. For this purpose, polyclonal antibodies to Cx31 and Cx45 were raised by immunizing rabbits with fusion proteins of glutathione S-transferase and carboxy-terminal peptides including 65 amino acids of Cx31 or 138 c-terminal amino acids of Cx45, respectively. Here we describe characterization of the affinity-purified Cx31 antibodies in human HeLa cells, transfected with mouse Cx31 coding DNA, and in mouse keratinocyte-derived cell lines. In the epidermis of embryonic mice at day 19 of gestation Cx43 and -45 were detected in the basal layer, while the stratum spinosum showed expression of Cx43, -31 and -26. In the stratum granulosum we found expression of Cx31 and -26. In the epidermis of adult mice Cx43 and -31 were located similarly as in embryonic tissue, but Cx45 as well as Cx26 were not detected and in addition Cx40 was weakly expressed in the stratum basale. Furthermore, during hair development, Cx31 was detected in the inner epithelial root sheath and sebaceous glands of hair follicle. Cx43 and -40 were found in the outer epithelial root sheath and to a lesser extent in sebaceous glands. Cx31 was also demonstrated in Hel-37 and Hel-30, i.e. two related cell lines derived from mouse keratinocytes. Our results show that epidermal and follicular differentiation coincides with differential expression of five different connexin proteins, suggesting specific and coordinated function(s) of gap junctional communication during skin and hair development.

Animals↗

PubMed1994

Immunochemical and electrophysiological characterization of murine connexin40 and -43 in mouse tissues and transfected human cells.

Human HeLa or SkHep1 cells, defective in intercellular communication through gap junctions, were transfected with coding sequences of murine connexin40 (Cx40) and -43. The transfected cells were restored in gap junctional coupling as shown by 100-fold increased electrical conductance. When studied by the double whole-cell patch-clamp technique, Cx40 HeLa transfectants exhibited single channel conductances of gamma = 121 +/- 7 pS and gamma = 153 +/- 5 pS. They were voltage gated with an equivalent gating charge of z = 4.0 +/- 0.5 for a voltage of half-maximal inactivation U0 = 44 +/- 7 mV. The corresponding values of connexin43 (Cx43) HeLa transfectants are: gamma = 60 +/- 4 pS and gamma = 40 +/- 2 pS as well as z = 3.7 +/- 0.8 and U0 = 73 +/- 7 mV. Transfer of the dye Lucifer Yellow was always considerably lower in Cx40- than in Cx43-transfectants though their total junctional conductance was similar or even higher than for Cx43-transfectants. In order to characterize cell and tissue distribution as well as phosphorylation of connexin40 and -43 proteins, antibodies to C-terminal oligopeptides of these proteins were prepared and used for immunoblotting, immunoprecipitation, and immunofluorescence analysis of transfected cells where they exhibited the punctate pattern characteristic of gap junctions on contacting membranes. Phosphorylation of connexin40 was shown by immunoprecipitation from 32P-labeled, transfected SkHep1 cells. Analyses of protein distribution in tissues revealed that the amount of connexin40 detected in heart was higher than in lung which is the inverse of the level of connexin40 mRNA in these tissues, suggesting posttranscriptional control of expression. Connexin40 protein in adult mouse heart and skin is about 20-fold more abundant than in the corresponding embryonic tissue. Connexin43 in adult mouse heart appears to be more highly phosphorylated than in embryonic heart or in transfected human cells.

Adenocarcinoma↗

PubMed1993

Effect of ramipril on alpha-adrenoceptor-mediated oscillatory contractions in tail artery of hypertensive rats.

Recent studies indicate that norepinephrine-induced contractile oscillations in the tail artery from stroke-prone spontaneously hypertensive rats (SHRSP) may be a vascular phenomenon independent of blood pressure level. The objectives of this study were: (1) to characterize pharmacologically the alpha-adrenoceptor mediating norepinephrine-induced oscillations in tail artery; and (2) to investigate the relationship between blood pressure level, altered by treatments with hydralazine/hydrochlorothiazide or the angiotensin converting enzyme inhibitor ramipril, and the observation of norepinephrine-induced oscillations in tail artery. The alpha 2-adrenoceptor agonists clonidine and guanabenz potently stimulated oscillatory contractions in the tail artery while the alpha 1-adrenoceptor agonists phenylephrine and methoxamine were considerably less potent. Yohimbine, an alpha 2-adrenoceptor antagonist, but not the alpha 1-adrenoceptor antagonist prazosin demonstrated high affinity for the receptor mediating norepinephrine-induced oscillatory contractions. These results support the hypothesis that norepinephrine-induced oscillatory contractions in the tail artery from SHRSP occur primarily through stimulation of alpha 2-adrenoceptors. Ramipril lowered blood pressure in SHRSP after 4 weeks of treatment during 6-10 weeks of life but did not alter the ability of the alpha 2-adrenoceptor agonist clonidine (10(-5) M) to induce contractile oscillations in tail arteries from SHRSP, indicating these oscillations are not a secondary effect of high blood pressure. These studies suggest that norepinephrine-induced oscillations in tail artery from SHRSP may be a vascular trait separate and distinct from blood pressure level and angiotensin II expression early in life.

Animals↗

PubMed1993

Spatial and temporal expression of connexin26 and connexin43 in rat endometrium during trophoblast invasion.

The expression of two different gap junction transcripts, connexin26 and connexin43, has been investigated in rat endometrium during implantation and early chorionic-allantoic placentation. An induction of connexin26 protein is detected locally in the epithelium of the implantation chamber prior to trophoblast invasion. At the same stage connexin43 is found exclusively in the primary decidual zone. By the sixth day of pregnancy the uterine epithelium of the implantation chamber has degenerated and the invading trophoblast is directly confronted with the developing decidua. Connexin26 is then detected in decidual cells accompanying the invading trophoblast, whereas connexin43 has spread through the decidual tissue up into the myometrial layers. This distribution pattern of connexin43 and connexin26 is maintained until at least Day 9 of pregnancy. In decidual cells adjacent to the trophoblast both connexins seem to be coexpressed in the same gap junctional plaque. In these early stages of pregnancy a clear correlation exists between levels of connexin43 mRNA and protein expression. In regard to connexin26 mRNA a similar correlation is found from Day 5 of pregnancy onward. The amount of mRNA on Day 4, however, does not correspond to the amount of connexin26 antigen in the endometrium at that stage. The spatial and temporal expression pattern of connexin26 accompanies the process of embryo implantation in the surrounding endometrium, pointing to a specialized function of these cells.

Animals↗

PubMed1993

Gap junction protein connexin40 is preferentially expressed in vascular endothelium and conductive bundles of rat myocardium and is increased under hypertensive conditions.

Gap junction channels consisting of connexin protein mediate electrical coupling between cardiac cells. Expression of two connexins, connexin40 (Cx40) and connexin43 (Cx43), has been studied in ventricular myocytes from normal and hypertensive rats. Polyclonal affinity-purified rabbit antibodies to Cx43 and Cx40 have been used for immunohistochemical analysis on frozen sections from rat heart. These studies revealed coexpression of Cx43 and Cx40 in ventricular myocytes. In addition, Cx40 is preferentially expressed in three distinct regions: first, in the endothelial layer of the heart blood vessels but not in the smooth muscle layer of the arteries; second, in the ventricular conductive myocardium, particularly in the atrioventricular bundle and bundle branches, where Cx43 is not observed; and third, in the myocyte layers close to the ventricular cavities. These results suggest that Cx40 is preferentially expressed in the fast conducting areas of myocardial tissue. Expression of both Cx40 and Cx43 was also found in immunoblots from normal and hypertensive rat myocardiocytes. Under hypertensive conditions (ie, in spontaneous hypertensive rats and in transgenic rats that exhibit hypertension due to expression of an exogenous renin gene), we found a 3.1-fold increase in Cx40 expression, compared with normal myocardium. Furthermore, we detected a 3.3-fold decrease in Cx43 protein level in transgenic hypertensive rats. The coexpression of Cx40 and Cx43 proteins in rat myocytes, their spatial distribution, and the increased amount of Cx40 protein during cardiac hypertrophy suggest that Cx40 may be involved in mediating fast conduction under normal and pathological conditions. The increased expression of Cx40 in hypertrophic heart may be a compensatory mechanism to increase conduction velocity.

Animals↗

PubMed1993

Differential expression of gap junction connexins in endocrine and exocrine glands.

We have investigated the expression of three gap junction proteins and their corresponding mRNAs by secretory cells of a variety of endocrine and exocrine rat glands. By immunostaining cryostat sections (indirect immunofluorescence) with antibodies against connexins (Cx) 26, 32, and 43 and by hybridizing total glandular RNA (Northern blot) with cRNAs for these proteins, we have found that several endocrine glands (pituitary, parathyroid, pancreatic islets, and adrenal) express Cx43, variable levels of Cx26, and no Cx32, whereas several exocrine glands (lacrimal gland, salivary glands, pancreas, prostate, and seminal vesicle) express high levels of Cx32 and variable levels of Cx26, but no Cx43. Thus, different sets of proteins comprise the gap junctions of endocrine and exocrine glands. Together with the findings that an endocrine gland (thyroid) that discharges secretory products extracellularly before releasing them in the vascular compartment expresses both Cx43 and Cx32 and that an exocrine gland (preputial gland) that has a pheromonal role expresses Cx43, these observations suggest that the differential expression of gap junction connexins may be required to specify the endocrine or exocrine differentiation of a secretory cell.

Adrenal Glands↗

PubMed1993

Angiotensin-converting enzyme inhibition during development alters calcium regulation in adult hypertensive rats.

Studies have shown that angiotensin-converting enzyme (ACE) inhibitor treatment in young genetically hypertensive rats prevents the full expression of blood pressure and vascular abnormalities in the adult. This model provides unique conditions with which to study the pathogenesis of altered Ca++ regulation. Normotensive (WKY) rats and stroke-prone spontaneously hypertensive rats (SHRSP) received at 6 to 10 weeks of age either ACE inhibitor (ramipril), hydralazine/hydrochlorothiazide or no treatment. At 17 weeks of age, rats were anesthetized, and vascular tissue was excised. Thoracic aorta challenged with 20 mM caffeine in Ca(++)-free buffer produced a phasic contractile response. The magnitude of this phasic response was used as a measure of Ca++ released from intracellular stores; a direct correlation between this phasic response and systolic blood pressure was observed. A concentration-response curve to Bay K8644 was performed on carotid arteries; a direct correlation of force development to Bay K8644 and systolic blood pressure was observed. All WKY groups showed lower blood pressure and force development in response to Bay K8644 than did SHRSP. Treatment with ramipril reduced blood pressure and force development in response to Bay K8644 in adult SHRSP, although not to levels of WKY rats, whereas WKY rats were unaffected by treatment. These data support the hypothesis that contractile responses to Bay K8644 in carotid arteries and caffeine in aorta parallel changes in systolic blood pressure. We conclude that alteration of Ca++ regulation in hypertension is directly related to elevated blood pressure and mediated by an angiotensin II-sensitive mechanism during development.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗

PubMed1993

On the mechanisms of cell uncoupling induced by a tumor promoter phorbol ester in clone 9 cells, a rat liver epithelial cell line.

It is known that in Clone 9 (C9) cells, intercellular gap junctional communication (IGJC) is rapidly blocked by the tumor promoter phorbol ester, 12-O-tetradecanoylphorbol-13-acetate (TPA), but it recovers spontaneously a few hours later and becomes refractory to TPA (Yada et al., J. Membr. Biol. 88, 217-232 (1985)). We now report that gap junctions between C9 cells contain at least two junctional proteins, connexin26 (Cx26) and connexin43 (Cx43), and that the TPA-induced changes in IGJC correlate temporally to changes in the state of phosphorylation of Cx43. The latter changes were prevented by inhibition of protein kinase C. Phosphoamino acid analysis and two-dimensional tryptic peptide maps of 32P-labeled Cx43 showed that during the TPA-induced phosphorylation at least two of the phosphorylated forms of Cx43 were differentially phosphorylated in seryl residues as compared to control. TPA induced a drastic reduction in junctional conductance as well as a redistribution of unitary gap junction channel event sizes seen in control cells. These changes were associated with retrieval of Cxs from the plasma membrane. Reappearance of gap junctions formed by Cx43 but not by Cx26 accounted for the spontaneous recovery in IGJC. It is proposed that gap junctions between C9 cells contain two types of channels each formed by Cx43 or Cx26 and that they are differentially affected during the action of TPA.

Animals↗

PubMed1992

Expression of connexins in the developing olfactory system of the mouse.

To gain insight into the function of gap junctions' connexin43, connexin32 and connexin26 in a neural structure that retains neuronal turnover capacities throughout adulthood, the expression of these molecules has been investigated in the developing and adult olfactory system by immunocytochemical and biochemical methods. Connexin43 was detectable from the olfactory placode stage. During early embryonic development, the levels of connexin43 expression remained low. An increase in the expression of this connexin occurred perinatally. Expression of connexin43 became very high during the postnatal stages and adulthood. Electron microscopy (EM) immunocytochemistry of the olfactory system showed connexin43 expression in non-neuronal cells. Strong regional differences in the expression of connexin43 in the olfactory epithelium were observed. No apparent relationship between connexin43 expression and turnover activity of olfactory neurons was detected. Western blots of olfactory tissues revealed the presence of three different isoforms of connexin43. Connexin32 was detected in the olfactory bulb at late postnatal stages including adulthood. Connexin32 was observed on some cells tentatively identified as oligodendrocytes. Connexin26 was localized onto leptomeninges. Some immunofluorescence was also obtained in the periglomerular region and in the subependymal layer of the bulb. Northern blot analysis revealed the presence of mRNA of connexin32 and connexin26 in the adult olfactory system. Our results substantiate the cell specific expression of these three types of connexins and they document the primary of connexin43 in olfactory tissues. Moreover, our findings indicate that although expression of connexin43 in the olfactory system is developmentally regulated, it is not directly associated with the neuronal cell turnover of the olfactory epithelium.

Animals↗

PubMed1992

Expression of Cx26, Cx32 and Cx43 gap junction proteins in normal and neoplastic human tissues.

This report concerns the expression of the gap-junction proteins Connexin (Cx)26, 32 and 43 in different malignant and non-malignant human tissues. Affinity-purified polyclonal antibodies against Cx26, 32 and 43 were used for immunohistochemical as well as immunoblot analysis. Cx32, the major gap-junction protein in rat and mouse liver, was detected in human liver and kidney. By contrast, Cx43 was expressed in epithelial and mesenchymal tissues and Cx26 was detected in different epithelia. Whereas all of the benign tumors studied, and some malignant ones, showed stable expression of gap-junction proteins, breast cancer, renal-cell cancer and sarcomas showed a significant decrease in gap-junction proteins as opposed to normal tissue. Cx43, not detected in human normal liver, was found in human hepatocellular carcinoma and Cx26, not detected in human adult skin, was observed in tissue samples of basal-cell carcinoma. In immunoblot analysis, Cx32 antibodies recognized a 27-kDa protein in human liver and hepatocellular carcinoma. A 43-kDa polypeptide was detected in human kidney, renal-cell carcinoma, normal breast, connective tissue of invasive-duct carcinoma of the breast and hepatocellular carcinoma.

Antibodies↗

PubMed1992

Characterization of gap junctions between osteoblast-like cells in culture.

The structure of gap junctions in osteoblast-like cells (OBs) and the connexins (cx) that build up these structures were characterized by ultrastructural, immunocytochemical, and molecular techniques. Ultrastructural studies revealed numerous gap junctions which were mostly located on processes of neighboring cells. Immunofluorescence labeling using two different antibodies (specific to mouse live cx26 and cx32 and to a peptide-specific rat heart gap junction protein cx43) gave evidence that in OBs, gap junctions consist mainly of cx43. The presence of cx43 in cultured OB was also confirmed by Western blot analysis. Dye-coupling with Lucifer yellow led to a staining of up to 30 neighboring cells. Parallel intracellular recordings showed that membrane potential amplitude changes (4-5 mV) are typically related to those in the coupled cells. Thus, there is morphological and functional evidence for intercellular communication between OB in culture. OBs in culture express the same connexins as observed in vivo and may serve as a model to investigate electrophysiological events in response to different stimulation signals.

Animals↗

PubMed1992

The hepatocyte-specific phenotype of murine liver cells correlates with high expression of connexin32 and connexin26 but very low expression of connexin43.

This investigation was initiated in order to find out whether expression of the hepatocyte-specific phenotype is accompanied by expression of certain connexin genes coding for gap junctional protein subunits. Several clones of mouse embryonic hepatocytes immortalized in serum-free MX83 medium by infection with recombinant retrovirus-expressed transcripts for connexin32, connexin26, albumin, alpha-fetoprotein, tyrosine aminotransferase, as well as aldolase A and B, at more than half of the levels found in primary mouse hepatocytes. In addition the immortalized hepatocyte clones contained low levels of connexin43 mRNA of which only trace amounts were detected in primary embryonic mouse hepatocytes and in rat liver. Two of the immortalized hepatocyte clones were shifted from serum-free MX83 medium to Dulbecco's modified Eagle medium (DMEM) containing 10% fetal calf serum and, after 2, 14, or 180 days, back to MX83 medium. We found that expression of connexin32 and connexin26 mRNAs as well as transcripts of other liver-specific proteins was reversibly decreased in serum-containing medium, whereas the expression level of connexin43 transcripts was increased in serum-containing DMEM compared to serum-free MX83 medium. The expression levels of connexin26, connexin32, or connexin43 mRNAs were altered by the addition of fetal calf serum or arginine or by the absence of hydrocortisone in MX83 medium, all of which contributed to the shift in phenotype. Furthermore several dedifferentiated cell lines derived from rat or mouse liver and cultivated in serum-containing medium were found to express little connexin32 or connexin26 mRNA but relatively high levels of connexin43 mRNA.

Animals↗

PubMed1991

Pinealocytes in rats: connexin identification and increase in coupling caused by norepinephrine.

Dye coupling was observed between pinealocytes in acutely dissected pineal glands of adult rats. Pinealocytes maintained in culture were also electrically coupled. Connexins 26 and 43 and their respective mRNAs were present but neither connexin32 nor its mRNA were detected. Pinealocytes expressed only connexin26 whereas connexin43 was confined to astrocytes. In 5-day-old cultures of pinealocytes the incidence of dye coupling and level of immunodetectable connexin26 were low, and both were increased by norepinephrine (NE). The increase in incidence of coupling was maximal at around 6 h after treatment and was prevented by inhibitors of protein or mRNA synthesis. NE-induced metabolic and electrical synchronization mediated by gap junctions may favor melatonin secretion.

Animals↗

PubMed1991

In vivo modulation of connexin 43 gene expression and junctional coupling of pancreatic B-cells.

We have explored the expression of gap junctional proteins and corresponding mRNAs by insulin-producing B-cells of native rat pancreas and of a transplantable rat insulinoma. By immunostaining cryostat sections (indirect immunofluorescence) and crude membrane preparations (Western blots) with antibodies against connexins 26, 32, and 43 and by hybridizing total islet and insulinoma RNA (Northern blot) with cRNAs for the latter two proteins, we have found that normal and tumoral B-cells express connexin 43 but do not show detectable levels of either connexin 32 or 26. By evaluating the conductance (dual patch-clamp whole-cell recording) and permeability of junctional channels (microinjection of Lucifer yellow), we have found that control B-cells show low levels of electrical and dye coupling in only a portion of the pairs studied. By studying B-cells of glibenclamide-treated rats, we have found that sustained stimulation of insulin release in vivo is associated with a two-fold increase in the level of connexin 43 gene transcripts and in the incidence of both ionic and dye coupling. These observations indicate that (1) connexin 43 is a major component of communicating channels between insulin-producing cells; (2) some but not all B-cells are electrically coupled by low conductance junctional channels; and (3) connexin 43 gene transcripts and incidence of junctional coupling are modulated in parallel during sustained stimulation of B-cell functioning in vivo.

Animals↗