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Biomedical subjects

G Guillon

Publications and source records attributed to G Guillon.

At least 109 records · Page 6Linked to original sources
PubMed1984

Plasma antidiuretic hormone levels and liver vasopressin receptors in the jerboa, Jaculus orientalis, and rat.

V1 vasopressin, angiotensin, alpha-adrenergic, and glucagon receptors in liver were studied on membrane fractions prepared from two groups of jerboas ( Jaculus orientalis) given dry or water-enriched diets for periods of 4 to 7 weeks, and from rats acutely treated with pharmacological amounts of arginine-vasopressin (AVP) or (1-deamino-8-D-arginine)-vasopressin (dDAVP). Tritiated (8-lysine)-vasopressin ([3H]vasopressin), tritiated (1-asparagine-5-valine)-angiotensin II ([3H]angiotensin II), tritiated dihydroergocryptine ([3H] DHEC ), and iodinated glucagon ([125I]-glucagon) were used as specific labeled ligands of these receptors. The V1 vasopressin, angiotensin, alpha-adrenergic, and glucagon receptors detected in both groups of jerboas were identical to receptors found in rat liver plasma membranes in regard to the apparent dissociation constants for their respective labeled ligands. Furthermore, vasopressin receptors in jerboa liver membranes discriminated as efficiently as rat liver receptors between the natural neurohypophyseal peptides arginine-vasopressin and lysine-vasopressin on the one hand and the structural analogs (1-deamino-8-D-arginine)-vasopressin and (4-valine-8-D-arginine)-vasopressin on the other. The reduction of antidiuretic hormone (ADH) secretion in jerboas fed a water-enriched diet compared to those on a dry diet (75 +/- 25 pM versus 372 +/- 86 pM) was accompanied by an increase in the number of liver vasopressin receptors (2.79 +/- 0.53 versus 1.25 +/- 0.14 pmol [3H]vasopressin bound/mg protein). The modifications observed were specific for vasopressin receptors, as judged by the maximal binding capacities of [3H]angiotensin II, [3H] DHEC , and [125I]-glucagon, which remained unchanged in jerboas whatever the levels of endogenous circulating ADH. Similarly, administration of pharmacological doses of AVP by iv infusion to rats induced, 2 hr later, a loss of about 50% of V1 liver vasopressin receptors, while the numbers and apparent dissociation constants of angiotensin, alpha-adrenergic, and glucagon liver receptors remained unchanged, and V2 kidney vasopressin receptors were almost desensitized. For V1 liver and V2 kidney vasopressin receptors, the desensitization process was strikingly dependent on the antidiuretic/glycogenolytic activity ratio of the peptide used. Thus, im injection to rats of dDAVP (an analog possessing a very high antidiuretic/glycogenolytic activity ratio) induced, 1 hr later, a total loss of V2 kidney receptors without modification of the number and apparent dissociation constant of V1 liver receptors.

Adenylyl Cyclases↗
PubMed1984

Reduction in hepatic but not in renal and vascular vasopressin receptor number in hyperinsulinemic mice and rats.

Hepatic plasma membranes of female obese mice C57 BL-6 orl ob/ob (ob/ob mice) completely lack vasopressin (VP) receptors of the V1 type whereas kidney VP receptors are normally expressed and functionally coupled to adenylate cyclase. To discover if these alterations are linked to a genetic defect of the V1 receptor, we have studied the binding of VP on liver and kidney membranes of two other models, female diabetic mice C57 BL-6 orl db/db (db/db mice) and female Zucker rats Fatty/orl fa/fa (fa/fa rats), which exhibit different temporal pattern of obesity, hyperinsulinemia and insulin resistance. In addition, since VP is known to exert its vascular response through stimulation of V1 receptors, we have studied the reactivity of VP of isolated tail artery in the three different models, ob/ob and db/db mice and fa/fa rats, and in their respective controls. In all cases, VP kidney receptors and VP vascular reactivity are normal. db/db mice exhibit a marked decrease in hepatic VP receptors whereas a 50% decrease was observed in 32 week fa/fa rats. Angiotensin II and prazosin binding sites are still present as well as the adenylate cyclase response to glucagon. These results suggest that the specific alteration in liver VP receptors is not related to a defect in V1 receptor genetic expression but is specific for liver and appears to parallel the level of hyperinsulinemia and/or insulin resistance.

Adenylyl Cyclases↗
PubMed1984

Angiotensin-induced changes in the apparent size of rat liver angiotensin receptors.

Angiotensin receptors from rat liver were labeled using four different ligands: (Sar1-(3H)Tyr4)-Angiotensin ll ((3H)SarAll); (Sar1-(3H)Tyr4-lle8)-Angiotensin ll ((3H)SarlleAll); (Sar1-(125I) Tyr4-(4'-N3) Phe8)-Angiotensin ll (IN3All); (Sar1-(125I)Tyr4-(4'N3D-Phe)8)-Angiotensin ll (IN3DPheAll). (3H)SarAll and IN3All behaved like agonists and (3H)SarlleAll and IN3DPheAll like antagonists. All four ligands labeled the same population of sites. The azido derivatives allowed covalent labeling of receptors with a high yield (about 40%). Membranes were solubilized by Triton X-100 under experimental conditions which ensured complete solubilization of the liganded receptors in a stable form (less than 40% dissociation after 20 h). The apparent size of liganded angiotensin receptors was determined by gel filtration on Ultrogel ACA-34 columns and by SDS gel electrophoresis (in the case of covalent labeling). The apparent Stokes radius of solubilized angiotensin receptors was different wether the receptor was labeled with an agonist (Stokes radius = 6.2 +/- 0.1 nm (6) after labeling with (3H)SarAll) or with an antagonist (Stokes radii of 5.5 +/- 0.1 (7), and 5.6 +/- 0.1 nm (4) after labeling with (3H)SarlleAll and IN3DPheAll respectively). After covalent labeling with IN3All angiotensin receptors were eluted as a mixture of light and heavy forms. SDS gel electrophoresis revealed only one molecular entity of Mr 64,000. It is concluded that binding of an agonist to liver angiotensin receptors triggers or stabilizes an interaction with another membrane component involved in the coupling of the receptor to its primary effector.

Angiotensin II↗
PubMed1984

Evidence for two molecular forms of solubilized vasopressin receptors in rat kidney membranes. Regulation by guanyl nucleotides.

As previously reported, it is possible to solubilize vasopressin-receptor complexes formed in rat kidney membranes by the use of Triton X-100. Ultracentrifugation on sucrose gradients and elution through molecular sieving columns of these soluble extracts revealed the existence of two molecular forms of vasopressin-receptor complexes (molecular weight = 200,000 and 100,000, respectively). These two molecular forms of vasopressin-receptor complexes can be partially purified and exhibit different properties: (a) The light form is more sensitive to thermal dissociation than is the heavy form. (b) The presence of guanyl nucleotide affects the dissociation rate of only the heavy form of the vasopressin-receptor complex. (c) The light form seems to be convertible to the heavy form by increasing the duration of incubation between the membranes and the tritiated hormone. (d) Guanyl nucleotides affect the distribution of the two molecular forms of the receptor (decrease of the relative amount of the heavy form). These data provide evidence for interaction between vasopressin-receptor complexes (light form) and another protein component, which may be a GTP-binding protein.

Animals↗
PubMed1980

Size of vasopressin receptors from rat liver and kidney.

Specific vasopressin receptors in rat liver membranes were recently characterized [Cantau et al., Journal of Receptors Research, in the press]. They differ from the receptors characterized earlier in kidney membranes as regards coupling with adenylate cyclase and specificity towards vasopressin structural analogues [Rajerison et al. (1974) J. Biol. Chem. 249, 6390-6400; Butlen et al. (1978) Mol. Pharmacol. 14, 1006-1017]. The object of the present work was to see whether these differences reflect a difference in the molecular size of liver and kidney vasopresin receptors. For this purpose, rat liver and kidney membranes were incubated with [3H]vasopressin and solubilized with Triton X-100 (0.3%). The properties of the macromolecular components of soluble extracts to which labelled vasopressin remained bound were observed to resemble those of the intact membrane receptors as regards binding reversibility at 30-37 degrees C and sensitivity to guanyl nucleotides. The hydrodynamic parameters of the soluble hormone-receptor complexes were estimated from Utrogel column filtration experiments and from sucrose density gradient ultracentrifugation experiments. The following values were obtained for liver and kidney receptors respectively: Stokes' radii: 5.4 and 5.6 nm; standard sedimentation coefficients: 3.7 and 3.7 S; partial specific volumes: 0.75 and 0.78 ml x g-1; molecular weight: 83000 and 80000. These results indicate that the marked functional differences between liver and kidney receptors are not accompanied by appreciable differences in molecular size.

Animals↗
PubMed1980

[Basal blood prolactin levels in male "infertility": measurements of limited value (author's transl)].

Systematic measurements of basal blood prolactin (PLR) levels were conducted in 383 patients with sperm anomalies or features of marital sterility of hyposterility, and 47 subjects consulting for sexual disorders. PRL levels were rarely abnormal in the patients in the two groups. Though systematic measurement of PRL levels should still be continued in patients with sexual disorders, the author refutes their usefulness in subjects consulting for sterility, their value in these cases being determined after the consultation and clinical examination, and, in some cases, by examination of the sperm.

Adult↗
PubMed1979

Cellular thorn-like projections in human endocervical epithelium. Preliminary scanning electron-microscopic study.

By means of scanning electron-microscopic investigations, thorn-like projections (TLP) were observed in the cilio-secretory epithelium of the ventral surface of the human endocervix. These projections, which seem to be characteristic of a new cell type, were seen at different stages of the menstrual cycle (days 8, 14 and 21) in 4 apparently healthy fertile women. Striking differences in length, with a maximum size at midcycle, suggest an evolutive process throughout the menstrual cycle. The origin and possible physiological role of TLP in the reproductive process are discussed.

Adult↗