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R Ardaillou

Publications and source records attributed to R Ardaillou.

At least 253 records · Page 14Linked to original sources
PubMedDate not supplied

Characterization of B2-bradykinin receptors in rabbit principal cells of the collecting duct.

Bradykinin (BK) plays a key role in collecting duct functions. Using an established line of principal cells of the rabbit collecting duct (R.C. SV3), we examined the characteristics of the BK receptors in these cells. [3H]-BK bound specifically to R.C. SV3. Saturation binding analyses allowed KD (968 +/- 232 pM) and Bmax values (356 +/- 43 fmol/mg protein) to be calculated. Competitive displacement of [3H]-BK was observed with Hoe-140, a specific type 2 BK receptor (BKR-2) antagonist, but not with des arg9-BK, a BKR-1 agonist. The presence of BKR-2 was confirmed by the reverse-transcription polymerase chain reaction technique. BK stimulated cytosolic calcium and inositol phosphate formation in a dose-dependent manner (from 1 nM to 1 microM). BK also inhibited the arginine vasopressin dependent increase of cyclic adenosine monophosphate. This effect could not be related to the production of prostaglandin E2. These results demonstrate the presence of high-affinity BKR-2 in the principal cells of the rabbit collecting duct that are linked to phospholipase C activity and are involved in arginine vasopressin related regulatory loops.

Animals↗
PubMedDate not supplied

Ecto-5'-nucleotidase of cultured rat mesangial cells.

Because adenosine plays a role in the regulation of glomerular filtration rate and of the release of renin, we examined the possibility of a local source for this mediator. We found that rat cultured glomerular mesangial cells converted 5'-AMP into adenosine. The properties of the enzyme involved in the reaction were those of an ecto-5' nucleotidase: (1) the products of the reaction were generated in the extracellular fluid although no 5'-nucleotidase was released by the cells into the medium; (2) identical activities were found for cultured cells in situ and sonicated cells; (3) the diazonium salt of sulfanilic acid which is a nonpenetrating reagent inhibited up to 75% of the enzyme activity. Ecto-5'-nucleotidase activity of intact cells obeyed Michaelis-Menten kinetics. Apparent Km for 5'-AMP was 0.32 mM. 5'-UMP was a strictly competitive inhibitor. ADP exerted a very powerful inhibitory effect and behaved also as a competitive inhibitor. ATP was inhibitory both by increasing Km and by decreasing Vmax. Ecto-5'-nucleotidase was active in the absence of divalent cations. However, Mg2+, Ca2+, Co2+ and Mn2+ were stimulatory. Zn2+ and Cu2+ suppressed the activity. Concanavalin A, a plant lectin, was markedly inhibitory, suggesting that a glycoprotein moiety was necessary to express enzyme activity. Ecto-5'-nucleotidase activity was not modified during phagocytosis of serum-treated zymosan by mesangial cells. Rat cultured glomerular epithelial cells exhibited a 5'-nucleotidase activity which was 4 times lower than that of the mesangial cells in primary culture.(ABSTRACT TRUNCATED AT 250 WORDS)

5'-Nucleotidase↗
PubMedDate not supplied

Characterization and control of expression of cell surface alkaline phosphodiesterase I activity in rat mesangial glomerular cells.

Membrane-bound nucleotidases and phosphodiesterases are critical regulators of extracellular nucleic acid processing. We previously demonstrated that mesangial cell 5'-nucleotidase was an ectoenzyme, the expression of which was stimulated by macrophage-secreted products. We show in the present study that rat mesangial cell alkaline phosphodiesterase I is also an ectoenzyme characterized by a Km value of 0.41 mM and a Vmax of 20.8 nmol min-1 mg-1. Treatment of mesangial cells by dexamethasone increased alkaline phosphodiesterase I activity in a dose- and time-dependent manner. Maximal increase (x1.5) occurred after treatment with 1 microM dexamethasone for 5 days. Cycloheximide and RU 38486, a glucocorticoid receptor antagonist, suppressed the dexamethasone-induced increase in alkaline phosphodiesterase I activity. 5'-Nucleotidase activity was not modified by dexamethasone under similar conditions of study. In contrast with 5'-nucleotidase, alkaline phosphodiesterase I expression remained unchanged in the presence of macrophage-conditioned medium or during cocultures of mesangial cells with macrophages. Interleukin-1, tumor necrosis factor, cyclic adenosine monophosphate and adenosine analogues also activated 5'-nucleotidase whereas they were inactive on alkaline phosphodiesterase I. These results suggest that extracellular DNA trapped in the mesangial area of the glomerular capillaries may be processed in part at the cell surface by alkaline phosphodiesterase I and that such an event may be regulated by glucocorticoids. They also show that alkaline phosphodiesterase I and 5'-nucleotidase obey a different regulation.

2-Chloroadenosine↗
PubMedDate not supplied

Vasopressin secretion during hyperglycemia in insulin-dependent diabetics.

Plasma levels of vasopressin (AVP) were measured in ten insulin-dependent diabetic patients before and during intravenous administration of hypertonic glucose. Plasma glucose and plasma osmolality increased from 12.4 +/- 1.2 to 47.0 +/- 2.3 mmol/l and from 293 +/- 2.0 to 307 +/- 2.8 mosm/kg respectively. Plasma vasopressin increased in parallel from 5.6 +/- 0.6 to 7.7 +/- 0.6 pg/ml. The present results demonstrate that hyperglycemia may be an effective stimulus for AVP secretion in insulin-deficient diabetics.

Adult↗
PubMedDate not supplied

[Hormonal stimulation after injection of thyrotrophin releasing factor (TRF) and 1-24 ACTH in patients following chronic treatment with neuroleptics (author's transl)].

Fifteen patients with neuroleptic treatment (haloperidol 4 to 6 mg a day or phenothiazines) and eleven control patients were given TRH 250 microgram i.v. and 1-24 ACTH, i.m. different times, TSH, T3, T4, FT4, Prolactin (PRL) cortisol were measured. Before TRH injection, at baseline, TSH is higher (p less than 0,01) and T3 lower (p less than 0,05) in the neuroleptics treated group than in the control group. These results suggest the occurrence of a biological hypothyroidism in the group with neuroleptics; moreover PRL is significantly increased. After TRH injection the response is not significantly different between the two groups. Cortisol level is lower at baseline and after 1-24 ACTH injections in the group with neuroleptics.

Adrenocorticotropic Hormone↗
PubMedDate not supplied

Release of cyclic nucleotides from the apical and basolateral poles of cultured human glomerular epithelial cells.

We have examined the intracellular accumulation and the release of cGMP and cAMP from the apical and basolateral poles of SV40-transformed human glomerular visceral epithelial cells (HGVEC) cultured on filters. After treatment of the cells by atrial natriuretic peptide (ANP), cGMP did not accumulate in the cells and was rapidly released mainly into the apical medium (86% of its total secretion). Its apical secretion was inhibited by 83% in the presence of probenecid, an organic acid transport inhibitor, and by 90% in the presence of nocodazole, a microtubule disrupter. cAMP was released more slowly than cGMP after it had accumulated in the cells. Apical polarization of the secretion still existed but was less marked than for cGMP (70% of its total secretion). Similarly, probenecid and nocodazole inhibited to a lesser degree cAMP egression (66 and 33%, respectively, for the apical secretion). Polarization of HGVEC was confirmed by the vectorialized secretion of lactate dehydrogenase. These results indicate that cGMP release from HGVEC is essentially apical and depends on a probenecid-sensitive organic acid transport and also on an intact microtubular network. cAMP release appears to be less polarized and less sensitive to the two drugs studied. Vectorially secreted cGMP in the urinary space in response to ANP could act downstream in the nephron and thus permit ANP to stimulate cells which do not necessarily possess ANP receptors.

Cell Line, Transformed↗