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S Jard

Publications and source records attributed to S Jard.

At least 73 records · Page 4Linked to original sources
PubMed1983

Lack of vasopressin receptors in liver, but not in kidney, of ob/ob mice.

The activity of phosphorylase a was measured in isolated hepatocytes from fed lean and ob/ob mice after addition of vasopressin, angiotensin, phenylephrine and glucagon. The binding of these hormones to purified liver plasma membranes was also determined. In hepatocytes of ob/ob mice, no increase in phosphorylase a was measured after addition of vasopressin, whereas the other hormones promoted an increase in the activity of the enzyme. No specific vasopressin receptors could be measured on purified liver plasma membrane of ob/ob mice. A decrease in the number of receptors for angiotensin and glucagon, without modification of the affinity, was also observed. No restoration of the number of vasopressin receptors was observed in liver of ob/ob mice starved for 3 days or in younger (5-6 weeks) animals. Vasopressin receptors and vasopressin-stimulated adenylate cyclase, measured on purified kidney medulla membranes, were similar in both lean and ob/ob mice. The data indicate a selective lack of vasopressin receptors and metabolic response in liver of the ob/ob mouse.

Animals↗
PubMed1983

Angiotensin II inhibits adenylate cyclase from adrenal cortex glomerulosa zone.

Angiotensin binding and the effects of angiotensin on adenylate cyclase activity were determined on purified membranes from the glomerulosa zone of bovine adrenal cortex. Angiotensin II inhibited adenylate cyclase activity in a dose-dependent manner with an A50-value of 2 nM. The angiotensin effect required the presence of GTP. Angiotensin also inhibited ACTH-stimulated activity. Angiotensin binding was sensitive to the same effectors which influenced angiotensin-induced adenylate cyclase inhibition. In the presence of NaCl 100 mM and magnesium, angiotensin interacted with a single population of binding sites (Kd = 4 nM and maximal binding capacity of 440 fmol/mg protein). These results and published data suggest that the ability to inhibit adenylate cyclase might be a general property of angiotensin receptors.

Adenylyl Cyclase Inhibitors↗
PubMed1983

Vasopressin and angiotensin II receptors in rat aortic smooth muscle cells in culture.

Rat aortic smooth muscle cells were isolated and maintained in primary culture. After 2-3 days, cells recovered their contractile phenotype and could be induced to contract in response to vasopressin and angiotensin II. Vasopressin- and angiotensin-specific binding sites were detected on these cells, using tritiated Lys8-vasopressin, Asn1-Val5-angiotensin II, and Sarc1-Ile8-angiotensin II. Vasopressin binding sites had Kd values of 30 and 12 nM for Lys8-and Arg8-vasopressin, respectively, and a maximal binding capacity of 25,000 sites/cell. They displayed several of the expected characteristics of vasopressin receptors involved in the vasopressor response in vivo. A highly significant correlation was found between the relative agonistic or antagonistic vasopressor potencies of a series of vasopressin structural analogues and their relative abilities to inhibit [3H]vasopressin binding to aortic smooth muscle cells. Specific binding sites for Asn1-Val5-angiotensin II and Sarc1-Ile8-angiotensin II had the following characteristics: Kd = 2.3 and 1.3 nM, respectively; maximal capacity: 50,000 sites/cell. Vasopressin and angiotensin did not modify the intracellular cyclic AMP content of aortic smooth muscle cells.

1-Sarcosine-8-Isoleucine Angiotensin II↗
PubMed1982

The liver angiotensin receptor involved in the activation of glycogen phosphorylase.

Specific angiotensin binding to rat hepatocytes and purified liver plasma membranes was measured by using biologically active [(3)H]angiotensin (sp. radioactivity 14Ci/mmol). The kinetic parameters for angiotensin binding to hepatocytes are: K(+1) (association rate constant). 100mum(-1).min(-1); K(-1) (dissociation rate constant), 2min(-1); K(d) (dissociation constant). 30nm; maximal binding capacity, 0.42pmol/10(6) cells or 260000 sites/cell. Angiotensin binding to membranes is profoundly affected by GTP (0.1mm) and NaCl (100mm); these regulatory compounds greatly enhance both the rate of association and of dissociation and also the extent of dissociation. K(d) amounts to 10nm in the presence of GTP+NaCl and to 1.5nm in their absence; maximal binding capacity is 0.70pmol/mg of protein, both with or without GTP+NaCl. The relative affinities of 11 angiotensin structural analogues were deduced from competition experiments for [(3)H]angiotensin binding to hepatocytes and to membranes (in the latter case, GTP + NaCl were not included, in order to study the higher affinity state of the receptor). These are highly correlated with their biological activity (activation of glycogen phosphorylase in hepatocytes). Binding to membranes occurs in the same concentration range as the biological effect. On the other hand, the existence of numerous spare receptors is suggested by the observation that binding of the agonists to hepatocytes requires 25-fold higher concentrations than those needed for their biological activity. These data clearly suggest that the detected binding sites correspond to the physiological receptors involved in the glycogenolytic action of angiotensin on rat liver.

Angiotensin II↗
PubMed1981

[Vasopressin isoreceptors in the liver and kidney: relationship between hormone binding and biological response].

Two type of vasopressin receptors can be distinguished on the basis of their relation to adenylate cyclase. V1 renal receptors are coupled to adenylate cyclase; V2 receptors, present, for example, in liver and blood vessels, are not coupled to adenylate cyclase. V1 and V2 receptors also differ with respect to their abilities to discriminate between several structural analogues of vasopressin. V1 and V2 receptors, present in several cellular and homologous acellular preparations (isolated hepatocytes and live membranes, renal cells in culture and renal membranes), have been characterized using tritiated vasopressin. Dissociation constants for vasopressin binding to intact cells are comparable to dissociation constants for binding to acellular preparations. In all systems studied, a marked amplification of the hormonal signal can be demonstrated.

Adenylyl Cyclases↗
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

(3H)-vasopressin binding to isolated rat hepatocytes and liver membranes: regulation by GTP and relation to glycogen phosphorylase activation.

Specific vasopressin binding to rat hepatocytes and rat liver membranes was measured using biologically active (3H)-Tyr2-Lys8-vasopressin (8.5 Ci/mM). In both systems, vasopressin binding was found to be time-dependent, reversible, and saturable. The kinetic parameters for vasopressin binding were: apparent dissociation constants (Kd): 4.9 nM and 15 nM; maximal binding capacities: 0.83 pmoles/mg protein and 2.10(5) sites/Cell for purified membranes and intact cells respectively. The relative affinities of 19 vasopressin structural analogues were deduced from competition experiments and compared to the previously determined glycogenolytic (or antiglycogenolytic) potencies of these analogues. For both agonists and antagonists, a highly significant correlation was demonstrated between pKd and pKa (or pKi) values, suggesting that the detected binding sites are the physiological receptors involved in the glycogenolytic action of vasopressin on the rat liver. The affinity of antagonists for binding to these receptors is the same for both membranes and cells. In contrast, agonists which bind to vasopressin receptor sites have a higher affinity for purified membranes than for intact cells (Kd membranes/Kd cells = 8 +/- 1). GTP (0.1mM) reduced the affinity of agonists but not of antagonists for binding to membranes and abolished the differences between Kd values for binding to hepatocytes and membranes.

Animals↗