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J F Cloix

Publications and source records attributed to J F Cloix.

53 records · Page 3Linked to original sources
PubMed1983

Plasma endogenous sodium pump inhibitor in essential hypertension.

The presence of circulating Na+ pump inhibitors was investigated in hypertensive subjects using inhibition of ouabain binding to the pump and of Na+, K+-ATPase activity as tests. Plasma extracts from nearly half the normotensive subjects who were offspring of hypertensive parents as well as the essential hypertensive subjects were potent inhibitors. Three fractions, extracted from plasma, exhibited ouabain-like properties concerning competition for binding, inhibition of the Na+, K+-ATPase and of Na+-dependent serotonin uptake by platelets. When injected intracerebroventricularly, one of these fractions also induces a rise in blood pressure, as does ouabain. These results demonstrate the presence in some plasma of digitalis-like substances.

Animals↗
PubMed1983

[Affinity chromatography for the detection of human endogenous inhibitor of NA+, K+ -ATPase].

Na+, K+ -ATPase was immobilized in an ovalbumin-glutaraldehyde polymer and was used for the purification by affinity chromatography of the endogenous Na+, K+ -ATPase inhibitor from human plasma and urine. The endogenous inhibitor is increased in plasma of hypertensive subjects in comparison with normotensive subjects. An increase of the inhibitor is also found in urine collected during a salt load in comparison with normal urine.

Chromatography, Affinity↗
PubMed1982

[Characteristics of membrane and plasma proteins in the spontaneously hypertensive rat].

The red blood cell membrane proteins and plasma proteins of normal and spontaneous hypertensive Rats were studied by uni- and bidimentional polyacrylamide gel electrophoresis. The amount of band 3 was observed to be significantly reduced in the red blood cell membrane of spontaneously hypertensive Rats. Plasma from these Rats contained two additional heatstable proteins, characterized by a molecular weight of 16,000 dalton and isoelectric points of 4.7 and 5.1. These changes may constitute biochemical changes genetically associated with hypertension.

Animals↗
PubMed1982

Phospholipid phosphorylation in erythrocyte of spontaneously hypertensive rats.

The rapid turnover of phosphoinositides within membranes suggests that these lipids play an important role in membrane function. Since various abnormalities have been described in the erythrocyte membrane of the spontaneously hypertensive rat (SHR) we have studied the turnover of phosphoinositides in the erythrocyte of SHR and age-matched normotensive Wistar-Kyoto rat (WKY). This was achieved by measuring the incorporation of 32P into inositol lipids after incubation of 1) intact erythrocytes with [32P]orthophosphate and 2) isolated ghost membranes with [gamma-32P]ATP. In both series of experiments more than 99% of the radioactivity incorporated into lipids was into the polyphosphoinositides diphosphoinositide (DPI) and triphosphoinositide (TPI). In both intact erythrocytes and ghost membranes, the levels of 32P incorporated into DPI and TPI were significantly different in SHR than in WKY. Further analysis of factors known to influence the labeling of DPI and TPI indicated that this could be ascribed to decreased activities of phosphatidylinositol kinase and/or DPI kinase, with respect to ATP as substrate. Moreover comparison of data obtained in intact cells with those obtained with ghost membranes suggests that within the SHR erythrocyte, membrane-cytosol interactions may occur that could also be responsible for the alteration of phosphoinositide labeling observed in hypertensive animals. Since phosphoinositides have been reported to be involved in the Ca2+-gating system of membrane, our findings could be associated with the abnormal Ca2+ binding and transport recently described in SHR erythrocyte.

Animals↗
PubMed1981

Human parathyroid gland adenylate cyclase activity: inhibition by 24,25-dihydroxycholecalciferol in vitro.

1. Plasma membranes were prepared from parathyroid adenomas in patients with primary hyperparathyroidism and from hyperplastic glands obtained from patients with chronic renal insufficiency. The basal and isoproterenol- or sodium fluoride-stimulated adenylate cyclase activities were measured in membranes in the presence of several vitamin D3 metabolites. 2. 24,25-Dihydroxycholecalciferol (10 and 1000 pmol/l) decreased isoproterenol- and sodium fluoride-stimulated adenylate cyclase activities in membranes prepared from parathyroid glands. 1,25-Dihydroxycholecalciferol (1000 pmol/l) inhibited the isoproterenol-stimulated adenylate cyclase activity. 25-Hydroxycholecalciferol and vitamin D3 had no effect on adenylate cyclase activities. Basal adenylate cyclase activity was not affected by any of th vitamin D3 metabolites tested. 3. These results indicate that 24,25-dihydroxycholecalciferol inhibits the isoproterenol- and sodium fluoride-stimulated adenylate cyclase activities in parathyroid tissues. Such an inhibition could explain the very rapid decrease in parathyroid hormone secretion after 24,25-dihydroxycholecalciferol administration that has been previously reported.

24,25-Dihydroxyvitamin D 3↗
PubMed1980

Renal parathyroid hormone-dependent adenylate cyclase in vitamin D-deficient rats. Inhibition by hydroxylated vitamin D3 metabolites.

The adenylate cyclase activation by bovine synthetic parathyroid hormone (bPTH) (1-34) was studied in vitro in kidney plasma membranes from D-deficient (D-Mb) or normal (D+Mb) rats. In D-Mb, the apparent affinity of parathyroid hormone (PTH) for membranes (170 +/- 30 nM) was significantly higher than that measured in D+Mb (55 +/- 5 nM). The maximum velocity of the PTH-stimulated adenylate cyclase was significantly higher in D+Mb than in D-Mb (163.0 +/- 13.7 and 93.4 +/- 6.7 pmol of cAMP/mg of protein/min, respectively). The action of vitamin D metabolites on the adenylate cyclase stimulation by PTH was then studied in vitro in D-Mb and D+Mb. In D-Mb, 25-hydroxyvitamin D3, 24,25-, and 1, 25-dihydroxyvitamin D3 significantly inhibited cAMP production in the presence of 0.87 microM of bPTH. Vitamin D3 had no effect. Maximal inhibition (86%) was observed for 1,25-dihydroxyvitamin D3. 1,25-Dihydroxyvitamin D3 decreased the maximum velocity of PTH-stimulated adenylate cyclase but did not modify the bPTH apparent affinity for D-Mb. The vitamin D3 metabolites tested did not modify the cyclase stimulation by isoproterenol, sodium fluoride, or 5'-guanylylimidodiphosphate. The presence of 1,25-dihydroxyvitamin D3 or 25-hydroxyvitamin D3 did not increase the (Na-K)-ATPase or the phosphodiesterase activities. In the presence of 1,25-dihydroxyvitamin D3 and bPTH, the apparent affinity of ATP for the catalytic moiety was not modified. The maximum velocity was decreased. These results suggest an in vitro interaction between hydroxylated vitamin D metabolites and kidney membranes PTH receptor.

24,25-Dihydroxyvitamin D 3↗
PubMed1976

Cholecalciferol metabolites binding in porcine parathyroid glands.

We studied the cytoplasmic and nuclear binding of 25-hydroxychole-calciferol and 1alpha,25-dihydroxycholecalciferol inside porcine parathyroid glands. Both sterols bind to cytoplasmic components, but a specific nuclear uptake was demonstrated only for 1alpha,25-dihydroxycholecalciferol. These findings support the hypothesis that mammalian parathyroid glands are a target organ for some cholecalciferol metabolites.

Animals↗
PubMed1976

Inhibition of bovine renal adenylate cyclase by urinary products.

The secondary hyperparathyroidism in uremic patients is due to the modification plasma electrolyte concentrations accompanied by a renal resistance to PTH action. We postulate that the retention of a uremic toxin could be at least partly responsible for this resistance. We have tested this hypothesis "in vitro" by measuring the action of Middle Molecules on the adenylate cyclase activity stimulated by NaF, PTH and isoproterenol.

Adenylyl Cyclase Inhibitors↗
PubMed1975

[Radiolabeling (125I) with high specific activity of the 1-34 N-terminal derivative of bovine parathormone without loss of biological activity].

Radiolabelling of 1-34 N terminal synthetic biological active fragment of bovine parathormone (1-34 bPTH) with high specific activity and without loss of biological activity was studied. Chloramine T and lactoperoxydase methods were used. To assess biological activity of 125I 1-34 bPTH labelled fragment, we use their ability to activate renal cortical adenylate cyclase. Our results show that enzymatic labelling method preserved the biological activity. With the chloramine T method it is possible to keep the biological activity by using DMSO.

Adenylyl Cyclases↗
PubMedDate not supplied

Plasma protein changes in primary hypertension in humans and rats.

To determine whether plasma protein changes may be associated with primary hypertension, we analyzed plasma proteins from essential hypertensive (EHT) patients and genetically hypertensive rats using two-dimensional electrophoresis. An additional plasma protein, having a molecular weight of 13,000 daltons and an isoelectric point of 4.5, was found in 82% of the patients with borderline or moderate hypertension (n = 29) and in all permanently hypertensive patients (n = 12). This protein was detected in 36% of normotensive (NT) subjects (n = 50). In the latter, the influence of family history, sex, and secondary hypertension were studied. Plasma proteins were also studied in spontaneously hypertensive rats (SHR). In all plasma from young male (n = 10) and female (n = 6) SHR, two additional proteins (molecular weight = 16,000 daltons, pHi = 4.7 and 5.1) were detectable. These plasma proteins were not detectable in male Wistar Kyoto rats (WKY) and in 50% of female WKY, and their frequency was 10% (n = 10) and 0% (n = 3) in normal male WKY and in male WKY rendered hypertensive by methylprednisolone, respectively. We conclude that these alterations of plasma proteins may be considered a biochemical feature of primary hypertension.

Adolescent↗