Drp1 is dispensable for apoptotic cytochrome c release in primed MCF10A and fibroblast cells but affects Bcl-2 antagonist-induced respiratory changes.

BACKGROUND AND PURPOSE: Dynamin-related protein 1 (Drp1) mediates mitochondrial fission and is thought to promote Bax/Bak-induced cytochrome c release during apoptosis. Conformationally active Bax, Bak and Bax/Bak-activating BH3-only proteins, such as Bim, are restrained by anti-apoptotic Bcl-2 proteins in cells that are 'primed for death'. Inhibition of Bcl-2/Bcl-xL/Bcl-w by the antagonist ABT-737 causes rapid apoptosis of primed cells. Hence, we determined whether Drp1 is required for cytochrome c release, respiratory alterations and apoptosis of cells that are already primed for death. EXPERIMENTAL APPROACH: We tested the Drp1 inhibitor mdivi-1 for inhibition of cytochrome c release in MCF10A cells primed by Bcl-2 overexpression. We measured ATP synthesis-dependent, -independent and cytochrome c-limited maximal oxygen consumption rates (OCRs) and cell death of immortalized wild-type (WT) and Drp1 knockout (KO) mouse embryonic fibroblasts (MEFs) treated with ABT-737. KEY RESULTS: Mdivi-1 failed to attenuate ABT-737-induced cytochrome c release. ABT-737 decreased maximal OCR measured in the presence of uncoupler in both WT and Drp1 KO MEF, consistent with respiratory impairment due to release of cytochrome c. However, Drp1 KO MEF were slightly less sensitive to this ABT-737-induced respiratory inhibition compared with WT, and were resistant to an initial ABT-737-induced increase in ATP synthesis-independent O2 consumption. Nevertheless, caspase-dependent cell death was not reduced. Pro-apoptotic Bax was unaltered, whereas Bak was up-regulated in Drp1 KO MEF. CONCLUSIONS AND IMPLICATIONS: The findings indicate that once fibroblast cells are primed for death, Drp1 is not required for apoptosis. However, Drp1 may contribute to ABT-737-induced respiratory changes and the kinetics of cytochrome c release.

[Day case laparoscopic sacral colpopexy for genital prolapse]. / Prise en charge ambulatoire de la promontofixation laparoscopique pour prolapsus génital.

OBJECTIVE: To demonstrate the feasibility of day case laparoscopic sacral colpopexy with the help of a fast tracking protocol. METHODS: Three motivated patients suffering from external cystocele have been strictly selected from September 2011 to October 2011 according to criteria such as Body Mass Index, ASA score, comorbidities et French day case rules. Laparoscopic sacral colpopexies consisted in anterior and posterior polyesther meshes sutured with non-resorbable wires. We are used to proceed through a SILS(©) unique ombilical port. We have used standard and straight laparoscopic instruments and laparoscope. The bladder catheter has been removed two hours after surgery, the patients have been encouraged to stand up and they have received a light meal before Chung score has been quoted. The patients have been discharged in the evening before 7 pm. RESULTS: The patients are 65, 67 and 66 years old, two of them had a past history of pelvic surgery. We did not deplore any complication during the procedure, no blood loss, no laparoscopic conversion (additional trocar); the procedures durations were 92, 120 and 124 min. These three patients have not been readmitted. Clinical examination has been scheduled between 6 and 8 weeks after surgery. We did not describe any pelvic or parietal complication, no early recurrence. CONCLUSION: We have demonstrated here the feasibility in good security conditions of day case laparoscopic sacral colpopexy for genital prolapse. A fast tracking protocol is essential and selecting the patients is required.

TP53INP1 decreases pancreatic cancer cell migration by regulating SPARC expression.

Tumor protein 53 induced nuclear protein 1 (TP53INP1) is a p53 target gene that induces cell growth arrest and apoptosis by modulating p53 transcriptional activity. TP53INP1 interacts physically with p53 and is a major player in the p53-driven oxidative stress response. Previously, we demonstrated that TP53INP1 is downregulated in an early stage of pancreatic cancerogenesis and when restored is able to suppress pancreatic tumor development. TP53INP1 downregulation in pancreas is associated with an oncogenic microRNA miR-155. In the present work, we studied the effects of TP53INP1 on cell migration. We found that TP53INP1 inactivation correlates with increased cell migration both in vivo and in vitro. The impact of TP53INP1 expression on cell migration was studied in different cellular contexts: mouse embryonic fibroblast and different pancreatic cancer cell lines. Its expression decreases cell migration by the transcriptional downregulation of secreted protein acidic and rich in cysteine (SPARC). SPARC is a matrix cellular protein, which governs diverse cellular functions and has a pivotal role in regulating cell-matrix interactions, cellular proliferation and migration. SPARC was also showed to be upregulated in normal pancreas and in pancreatic intraepithelial neoplasia lesions in a pancreatic adenocarcinoma mouse model only in the TP53INP1-deficient animals. This novel TP53INP1 activity on the regulation of SPARC expression could explain in part its tumor suppressor function in pancreatic adenocarcinoma by modulating cellular spreading during the metastatic process.

Reg genes are CCK2 receptor targets in ElasCCK2 mice pancreas.

We previously demonstrated that expression of the gastrin receptor, CCK2R, in pancreatic acini of transgenic ElasCCK2 mice induced alteration of acinar morphology and differentiation, increased sensitivity to a carcinogen and development of preneoplastic lesions and tumours. Reg proteins are suggested to be involved in pancreatic cancer and in regeneration of endocrine pancreas. Reg I gene is a known target of gastrin. We examined whether an expression of CCK2R in the pancreatic acini of ElasCCK2 mice is linked to induction of Reg proteins expression. We analyzed Reg expression by Western-blot and immunohistochemistry in pancreas from ElasCCK2 and control mice. Islet neogenesis, glucose homeostasis, insulin secretion and content were also evaluated. Reg I is exclusively produced in acini in ElasCCK2 and control mice. In tumoral pancreas, Reg I and Reg III proteins are expressed in duct-like cells in preneoplastic lesions or in the periphery of tumours and in adjacent acini. The expression of Reg III proteins is increased in ElasCCK2 pancreas before the development of preneoplastic lesions in a subpopulation of islet cells and in small islet-like cell clusters dispersed within the acinar tissue. Several criteria of an enhanced neogenesis are fulfilled in ElasCCK2 pancreas. Moreover, ElasCCK2 mice have an improved response to glucose load, an increased insulin secretion and a doubling of insulin content compared to control mice. We show that Reg proteins are targets of CCK2R activation and are induced during early steps of carcinogenesis in ElasCCK2 mice pancreas. Alterations of exocrine tissue homeostasis in ElasCCK2 pancreas concomitantly activate regenerative responses of the endocrine pancreas possibly linked to paracrine actions of Reg III proteins.

Cholecystokinin-2 receptor modulates cell adhesion through beta 1-integrin in human pancreatic cancer cells.

Several lines of evidence suggest that gastrin and the CCK-2 receptor (CCK2R) could contribute to pancreatic carcinogenesis by modulating processes such as proliferation, cell adhesion or migration. In the current study, we used a 'cancer gene array' and identified beta1-integrin subunit as a new gastrin-regulated gene in human pancreatic cancer cells. We also demonstrated that Src family kinases and the phosphatidylinositol-3-kinase (PI-3-kinase) pathway play a crucial role in the expression of beta1-integrin induced by gastrin. Our results also showed that gastrin modulates cell-substrate adhesion via beta1-integrin. Indeed, using blocking anti-beta1-integrin monoclonal antibodies, we completely reversed the increase in cell-substrate adhesion induced by gastrin. In addition, we observed that in response to gastrin, beta1-integrin is tyrosine phosphorylated by Src family kinases and associates with paxillin, a scaffold protein involved in focal adhesion and integrin signalling. This mechanism might be involved in gastrin-induced cell adhesion. Moreover, we showed in vivo that targeted CCK2R expression in the pancreas of Elas-CCK2 mice leads to the overexpression of beta1-integrin. This process may contribute to pancreatic tumour development observed in these transgenic animals.

Pulse pressure, endothelium function, and arterial stiffness in spontaneously hypertensive rats.

In rats, removal of the carotid arterial or abdominal aortic endothelium results in an acute increase of diameter and compliance. In humans, acute local administration of a specific NO synthase inhibitor increases radial artery compliance but not the diameter. The purpose of this review is to determine whether in spontaneously hypertensive rats (SHR), a cause-and-effect relationship may be observed between endothelial function and arterial stiffness with possible consequences on pulse pressure (PP) control. The study is based on a comparative time-dependent analysis of the following in young and old SHR: aortic blood pressure measurements and reactivity, ultrasonographic arterial stiffness assessment, aortic histomorphometry and staining, and molecular biology with evaluation of endothelium function. In young SHR, aortic mean blood pressure and PP increase proportionally, whereas isobaric arterial stiffness is unchanged or poorly modified. The endothelial NO response to norepinephrine is normal or upregulated as a response to predominant vasoconstrictive influences. In contrast, in old SHR, PP and mean blood pressure change disproportionately with age, together with an enhanced isobaric arterial stiffness. The endothelial NO response to norepinephrine is abolished, in association with endothelium-dependent heightened norepinephrine reactivity and enhanced accumulation of vessel extracellular matrix. In this latter case, exogenous NO acutely and selectively lowers the increased PP. Thus, during SHR aging, a negative feedback may be observed between NO bioactivity and PP through changes in arterial structure and function. Whether this alteration contributes to the development of systolic hypertension in old populations remains to be determined.

Tsix-mediated repression of Xist accumulation is not sufficient for normal random X inactivation.

During the X inactivation process, one X chromosome in each female embryonic cell is chosen at random to become coated by Xist RNA and silenced. Tsix, a transcript anti-sense to Xist, participates in the choice of the inactive X and in Xist regulation through as yet unknown mechanisms. Undifferentiated female ES cells, which have two active Xs, recapitulate random X inactivation when induced to differentiate. A 65 kb deletion targeted to one of the two Xs in a female ES cell line, and including both the end of the Xist gene and the site of initiation of Tsix, resulted in the exclusive inactivation of the deleted X in differentiated ES cells. We have re-examined the phenotype of the 65 kb deletion and targeted Tsix and the terminal exons of Xist back to the deleted locus using a cre/loxP site-specific re-insertion strategy. We show that prior to inactivation the deleted X is associated in undifferentiated ES cells with both increased Xist expression and diffusion of the Xist transcript away from its site of synthesis. Restoration of Tsix repressed the steady-state level of Xist expression and restricted Xist RNA to its transcription site. At the onset of inactivation in differentiated ES cells, restoration of Tsix failed to restore random X-inactivation, even though the levels of Xist RNA accumulation in cis were markedly reduced. These results identify for the first time a dual function for Tsix as both a repressor of the steady-state level of Xist expression and as a regulator of the distribution of Xist RNA within the nucleus. They also establish that random inactivation requires mechanisms additional to the in cis repression of XIST:

Pulse pressure, aortic reactivity, and endothelium dysfunction in old hypertensive rats.

The reactivity of old hypertensive rat aortas has not been investigated in relation to each phenotype of the blood pressure curve, mean arterial pressure (MAP), and pulse pressure (PP). Aortic reactivities from 3- to 78-week-old Wistar-Kyoto rats (WKY) and spontaneously hypertensive rats (SHR) were studied with the use of organ chambers and invasive blood pressure, carotid diameter, and histomorphometry. MAP and PP were elevated in SHR, but at 78 weeks, a selective increase of PP without further MAP increase was observed for the same carotid diameter as WKY. Aortic relaxation in response to carbamylcholine decreased similarly with age in both strains. With (+) or without (-) endothelium (E), maximal developed tension (MDT) under KCl increased linearly with age in SHR, proportionally to wall thickness and MAP increase. Under norepinephrine (NE), MDT of E(-) aortas from SHR and controls increased with age and reached plateaus at 12 weeks, whereas MDT of E(+) aortas from SHR increased linearly with age. Because the NE-induced MDT was higher for E(-) than E(+), the difference estimated endothelial function. This difference reached plateaus from 12 to 78 weeks in WKY but was abolished beyond 12 weeks in SHR, a finding also observed under NO-synthase inhibition. In old hypertensive rats, (1) increased KCl reactivity is endothelium independent but influenced by the MAP-dependent aortic hypertrophy with resulting increased vascular smooth muscle reactivity, whereas (2) increased NE reactivity is endothelium dependent in association with increased PP, altered endothelial function, and extracellular matrix, with resulting enhanced intrinsic arterial stiffness.

Acute and chronic sympathoinhibition on carotid artery diameter of spontaneously hypertensive rats: effects of clonidine and flesinoxan.

1. Hypertensive conduit arteries are thicker and stiffer than those of normotensive controls. Whether they are specifically sensitive to central sympathoinhibition has never been investigated. 2. The effects of acute (24 h infusion) and chronic (4 week infusion) treatments with clonidine (0.01 and 0.1 mg/kg per day) and flesinoxan (1 and 3 mg/kg per day) on carotid artery diameter were investigated in spontaneously hypertensive rats. At the end of treatment, blood pressure (BP) was recorded in the rats while they were conscious. Rats were then anaesthetized for carotid artery diameter measurements using an ultrasonic echotracking device. 3. In conscious rats, clonidine significantly decreased BP and heart rate (HR) following acute but not chronic treatment. In contrast, flesinoxan significantly decreased BP following both the acute and chronic treatment. In anaesthetized animals, the two agents have opposite effects on isobaric carotid artery diameter, with a decrease under clonidine and an increase under flesinoxan. After 4 weeks infusion, the reactivity of aortic rings was studied in organ chambers. Flesinoxan, but not clonidine, caused the relaxation of potassium chloride precontracted aortic segments. 4. The results indicate that although clonidine and flesinoxan are centrally acting antihypertensive agents, the drug-induced changes in isobaric carotid diameter may be influenced by local factors independent of the central action of the two drugs.

[Herpes labialis and genitalis in general medicine]. / Herpès labial et génital en médecine génrale.

OBJECTIVE: The purpose of this study was to determine the respective importance of herpes labialis and genitalis in patients consulting general practitioners and ascertain their knowledge and opinions concerning herpes labialis and genitalis in order to analyze patient behavior in case of flare-ups. PATIENTS AND METHOD: A questionnaire was proposed to a representative sample of patients aged 15 years and older seen at consultation by 49 general practitioners participating in the General Medicine Observatory of the French Society of General Practitioners. RESULTS: Among the 4,403 patients who responded, a known history of herpes labialis was reported by 39. 9 p.100 and of herpes genitalis by 2.5 p.100. Their answers to the questions demonstrated insufficient knowledge of avoidable risks of herpes as a sexually transmitted disease, with very significant misunderstanding by men. Among the 1,711 patients who had experienced herpes labialis, 62.9 p.100 initiated self-medication, 29 p.100 preferred to wait and see and 7.5 p.100 sought medical assistance. Among the 108 patients who had experienced herpes genitalis, at the last flare-up 40 p.100 initiated self-medication, 7.5 p.100 preferred to wait and see and 52 p.100 sought medical assistance. The general practitioner was the first physician consulted for both types of herpes. DISCUSSION: This study illustrates the importance of herpes infections in the general medicine patients. It also confirms that new interventional strategies are needed both for health care and for health education.

Usefulness of three-dimensional echocardiography for the evaluation of mitral valve prolapse: an intraoperative study.

BACKGROUND AND AIM OF THE STUDY: The study aim was to evaluate the feasibility of intraoperative three-dimensional (3D) transesophageal echocardiography (TEE) in patients referred for mitral valve prolapse (MVP) repair and to compare two-dimensional (2D) TEE and 3D TEE and surgical findings. METHODS: Forty-six patients (mean age 67 +/- 11 years) underwent 3D TEE intraoperatively. Measurements were made of the posterior part of mitral annulus circumference (PMAC), and the width of mitral valve surgical resection on the mitral annulus (WMVR). Using 3D TEE, MVP topography was described, and PMAC in diastole and the width of implantation of MVP on the mitral annulus (WMVP) in systole were measured. RESULTS: 3D TEE was successful in 42 patients (91%). 2D and 3DTEE correctly predicted MVP localization in 38 (90%) and 36 (86%) patients, respectively (p = NS). 3D TEE and surgical PMAC were 89 +/- 13 and 93 +/- 21 mm, respectively (p = 0.01, R = 0.42). WMVR and WMVP were 28 +/- 11 mm and 26 +/- 11 mm, respectively (p <0.0001, R = 0.82). WMVR/anatomic PMAC (0.29 +/- 0.11) and WMVP/3D echo PMAC (0.32 +/- 0.11) were correlated (p <0.0001, R= 0.69). CONCLUSION: Intraoperative 3D TEE evaluation of MVP is feasible. MVP width and its ratio to the mitral annulus were assessed, and found to correlate with surgical findings. These 3D data may be of value to the surgeon when performing mitral valve repair.

Relaxation of vascular smooth muscle by cicletanine in aged wistar aorta under stress conditions: importance of nitric oxide.

The vascular mechanism of action of cicletanine, an antihypertensive agent, was studied on isolated Wistar rat aortas (24-months-old) in presence and in absence of endothelium in two different stress conditions, normoxic and hypoxic, in presence of norepinephrine (NE). Under normoxic conditions, in presence of endothelium, cicletanine (10(-9)-10(-5)M) induced a concentration-dependent relaxation, whereas in absence of endothelium, cicletanine (10(-9)-10(-5)M) was ineffective although it relaxed the smooth muscle at higher concentrations (10(-4)M). At pharmacologic concentrations (below or equal 10(-5)M), relaxation induced by cicletanine, in presence of endothelium, was prevented by N(omega)-nitro-L-arginine (L-NNA) (P <.005) and relaxation induced by the highest concentration (10(-4)M) was reversed by BaCl2 (P <.005). Under hypoxic conditions, in presence of NE and endothelium, the aorta displayed an increased developed tension that was significantly (P <.05) attenuated by cicletanine (10(-5)M) and insensitive to indomethacine (10(-7)M). When the two compounds were added together, the relaxation induced by cicletanine was significantly improved (P <.005). These results indicated that cicletanine, under stress conditions, relaxes vascular smooth muscle through an endothelium-dependent action mediated by the nitric oxide (NO) synthase pathway. We proposed that the observed vascular effects could be associated with the counter-regulation mechanisms linked to the antihypertensive action of cicletanine.

Genetics. Reprogramming X inactivation.

Inactivation of one of the two X chromosomes occurs in all cells of female adult mice so that genes are expressed from only one X chromosome. In a Perspective, Clerc and Avner describe an elegant series of experiments in mouse embryos cloned from adult and embryonic female cell nuclei (Eggan et al.) that reveal how the inactivation state of the X chromosomes is reprogrammed.

The CCKB/gastrin receptor is coupled to the regulation of enzyme secretion, protein synthesis and p70 S6 kinase activity in acinar cells from ElasCCKB transgenic mice.

In order to determine which physiological functions can be regulated by the pancreatic CCKB/gastrin receptor, studies were carried out on pancreatic acini from mice expressing transgenic CCKB/gastrin receptors in the exocrine pancreas (ElasCCKB mice). Acini were stimulated by sulfated gastrin in the presence of SR 27897 (1.8 microM), blocking endogenous CCKA receptors. After 30 min incubation with gastrin, the secretion of chymotrypsinogen and amylase showed superimposable monophasic dose-response curves. Enzyme secretion was detectable and maximal at 100 pM and 1 nM of gastrin, respectively. No increase in chymotrypsinogen and amylase mRNAs was detected for doses of gastrin which specifically occupy the CCKB/gastrin receptor. In contrast, gastrin stimulated total protein synthesis in isolated acini from ElasCCKB mice. [35S]Methionine incorporation into total proteins was increased dose-dependently to a maximum for 30 pM gastrin and inhibited with higher doses (> 300 pM). Gastrin stimulated p70 S6 kinase activity for concentrations ranging from 10 pM to 1 nM. Gastrin-stimulated p70 S6 kinase activity and protein synthesis were blocked by rapamycin and wortmannin. Therefore, in ElasCCKB mice acinar cells, the CCKB/gastrin receptor mediates enzyme release and protein synthesis. However, a more efficient coupling of the CCKB/gastrin receptor to protein synthesis than to enzyme secretion was demonstrated. CCKB/gastrin receptor-stimulated protein synthesis likely results from an enhancement of mRNA translation and involves phosphatidyl inositol 3-kinase and p70 S6 kinase.

Evidence for a common defect associated with pressure in the aorta of two hypertensive rat strains.

1. Thoracic aortas of normotensive (Wistar-Kyoto (WKY) and Lyon normotensive (LN)) and hypertensive (spontaneously hypertensive rats (SHR) and Lyon hypertensive (LH)) rats from two groups (Japanese (WKY rats and SHR) and Lyon (LN and LH rats)) were compared using organ chambers. Changes in endothelium and smooth muscle reactivity to noradrenaline (NA), carbamylcholine and N omega-nitro-L-arginine (L-NNA) were analysed to distinguish between changes in reactivity that are associated with the presence of hypertension and those that are dependent on group (Japanese vs Lyon). 2. Aortas of hypertensive rats had lower pD2 values for NA than aortas from normotensive rats. These differences were associated with hypertension (P < 0.005 and P < 0.01) and group (P < 0.005 and P < 0.005) in presence or absence of endothelium, respectively, whereas no difference was seen in the maximal developed tension in response to NA. 3. Aortas also differed by a reduced ability to relax in response to carbamylcholine in hypertensive rats; this effect is hypertension (P < 0.05) and group (P < 0.005) dependent, without any change in carbamylcholine pD2 values. 4. Changes in maximum developed tension in the presence of L-NNA were found to be endothelium dependent and pressure and group independent. Furthermore, the change in tension induced by L-NNA appears significantly more pronounced in SHR than in LH rats (P < 0.05). 5. These results indicate that the common defect associated with hypertension appears to be linked to the endothelium through alpha-adrenoceptors and muscarinic receptors in both the Japanese and Lyon groups. However, SHR differs markedly from LH rats by having a higher developed tension in response to NA, this increased tension being counterbalanced by the release of nitric oxide, as observed in the presence of L-NNA.

Differences in aortic response to vasoactive stimuli in Japanese and Lyon rats. The role of hypertension.

OBJECTIVE: We have previously shown that conduit arteries of normotensive (WKY) and hypertensive (SHR) Japanese rats differ from normotensive (LN) and hypertensive (LH) Lyon rats in terms of lower aortic thickness and higher collagen III content, whereas differences in vasoactive properties are unknown. METHODS: Aortic rings with (E+) and without (E-) endothelium were studied under resting and noradrenaline-stimulated conditions in the presence of N(omega)-nitro-L-arginine (L-NNA) alone or in association with indomethacin, bosentan and/or BQ123. RESULTS: Under resting conditions, aortas of normotensive and hypertensive Japanese rats differed from Lyon rats by higher developed tension in the presence of L-NNA and endothelium. In the absence of endothelium, normotensives differed from hypertensives in terms of stronger developed tensions in the presence of L-NNA in the two strains. Addition of indomethacin to L-NNA induced relaxation in E+ SHR and E- WKY and contraction in E-LH. By contrast, tensions were unchanged after addition of bosentan and BQ123. Under stimulated conditions, tensions were equally increased by L-NNA in E+ and unchanged in E- both in Japanese and Lyon rats whether they were normotensive or hypertensive, and indomethacin (but not bosentan) elicited higher response in Lyon than in Japanese rats in E+ and E- aorta. CONCLUSION: Under NO synthase inhibition, the vasoactive properties of Japanese and Lyon aorta differ in the presence of a cyclo-oxygenase blocker but not endothelin blockers. These results indicate that the aorta vasorelaxant tone is associated to prostanoid regulation in Lyon but not in Japanese rats. This observation appears dependent on the genetic and/or environmental background linked to the origin and not the presence of hypertension.

Evidence for a functional role of the cholecystokinin-B/gastrin receptor in the human fetal and adult pancreas.

Gastrin (G) and cholecystokinin (CCK) are gastrointestinal neuropeptides that are released into circulation during a meal. G is also transiently expressed during embryogenic and early ontogenic development of the pancreas and is believed to act on islet-cell development. Both peptides act on pancreatic endocrine function; however, the effects are dependent on the species and on cellular and molecular underlying mechanisms that remain poorly characterized. Since CCK-B/G subtype receptor is predominant over the CCK-A subtype in the human pancreas, we hypothesized that it could be expressed by islet cells. Here we present reverse transcription-polymerase chain reaction and immunohistochemistry data demonstrating that the CCK-B/G receptor is expressed in islet cells and that islet glucagon-producing cells are the major site of CCK-B/G receptor expression in adult and fetal pancreas. Moreover, G immunoreactivity was detected in the fetal human pancreas at embryogenic week 22. G- and CCK-stimulated glucagon are released from purified human islets. Concentration of CCK and G eliciting a half-maximal level of glucagon secretion were 13 +/- 6 and 8 +/- 5 pmol/l, respectively. Maximal glucagon secretion was achieved in the presence of 30 pmol/l peptides and was similar to that obtained in the presence of 10 mmol/l L-arginine (1.6 pmol x ml(-1) x 90 min(-1)). The nonpeptide antagonist of the CCK-B/G receptor, RPR-101048, fully inhibited CCK- and G-stimulated glucagon secretion at 100 nmol/l concentration. These data are consistent with the view that the CCK-B/G receptor is involved in glucose homeostasis in adult humans and mediates the autocrine effects of G on islet differentiation and growth in the fetal pancreas.

[Mechanism of action of cicletanine on the relationship between endothelium and vascular smooth muscle in the rat thoracic aorta under normoxic and hypoxic conditions]. / Mode d'action du ciclétanine sur la relation endothélium-muscle lisse vasculaire de l'aorte thoracique de rat en conditions normoxiques et hypoxiques.

OBJECTIVE: The vascular mechanism of action of cicletanine, an antihypertensive agent, was studied on isolated Wistar rat aorta in presence and in absence of endothelium both in normoxic and hypoxic conditions. DESIGN AND METHODS: Isolated aorta, from 24 month-old rats, were precontracted with noradrenaline (10(-7) M), in presence and in absence of endothelium and exposed to cumulative cicletanine concentrations in presence and absence of either L-NNA (10(-4) M) or indomethacin (Indo) (10(-7) M). Thereafter, aorta were precontracted by noradrenaline 10(-7) M, and hypoxia was induced by switching gas mixture from 95%O2/5%CO2 to 95%N2/5%CO2 during 10 minutes. Results are expressed as mean +/- sem and statistical analysis were done using one-way analysis of variance. RESULTS: When aorta were precontracted with noradrenaline (10(-7) M), in presence of endothelium, cicletanine (10(-9)-10(-4) M), induced a biphasic concentration-dependent relaxation (EC50 approximately 10(-7) M and 3 x 10(-5) M). In absence of endothelium, the effect of cicletanine was abolished (10(-9) and 10(-5) M). Whereas, at higher concentration (10(-4) M), the magnitude of the relaxation reached 94 +/- 2% and 67 +/- 5% of the initial developed tension in presence and in absence of endothelium respectively. The endothelium-dependent relaxation induced by cicletanine was significantly reduced by Indo (10(-7) M) (p < 0.05) and L-NNA (10(-4) M) (p < 0.005). Addition of 10 mM of BaCl2 significantly reversed the relaxation induced by the higher concentration of cicletanine used (p < 0.005). Under hypoxic conditions, the aorta, in presence of endothelium, displayed an increased developed tension which was significantly attenuated by cicletanine. CONCLUSION: These results indicated that cicletanine relaxes vascular smooth muscle through both, an endothelium-dependent action which was mediated by cyclooxygenase and NOsynthase pathways and an endothelium-independent action that was mediated through K+ channels opening. Under hypoxic conditions, our findings indicate that the effects of cicletanine, appear related to an endothelium protective action associated to NO release.