[In vivo effects of 24R,25-dihydroxyvitamin D3 on kidney alkaline phosphatase and gamma-glutamyltransferase of hypophysectomized rats]. / Effets in vivo de la 24R, 25-dihydroxyvitamine D3 sur la phosphatase alcaline et la gamma-glutamyltransférase du rein de rats hypophysectomisés.

The effects of 24R, 25-dihydroxyvitamin D3 (24, 25 (OH)2 D3) on alkaline phosphatase (ALP), gamma-glutamyltransferase (GGT) and acid phosphatase (ACP) activities were investigated on renal cortex of hypophysectomized (Hx) rats. ALP activity was increased by +27, +56 and +60% as compared to controls respectively 3, 6 and 12 h after intraperitoneal administration of the secosteroid (10 pmoles/100 g body weight). Stimulations of GGT activity began only after 6 h (+30%) and 12 h (+ 46%). ACP activity was not modified. In vivo, the two enzymatic inductions in kidneys of Hx rats were higher and longer than those obtained in vitro.

[In vitro effects of 24R,25-dihydroxyvitamin D3 on alkaline phosphatase and gamma-glutamyltransferase in the kidney of hypophysectomized rats]. / Effets in vitro de la 24R,25-dihydroxyvitamine D3 sur la phosphatase alcaline et la gamma-glutamyltransferase du rein de rat hypophysectomisé.

The effects of 24R,25-dihydroxyvitamin D3 (24,25-(OH)2D3 on alkaline phosphatase (PAL), gamma-glutamyltransferase (GGT) and acid phosphatase (PAC) activities were investigated on renal cortex slices of hypophysectomized rats. Indeed after hypophysectomy renal 24,25-(OH)2D3 production was increased and renal PAL and GGT activities were decreased. After 5h incubation with physiological concentrations (0.1-10 nM) of 24,25-(OH)2D3 significant increases of PAL and GGT activities were produced. The maximum stimulation obtained with 1 nM was +23% for PAL and +26% for GGT as compared to controls. PAC was not modified. The time course of these effects was studied from 45 min to 8 h. In the presence of 24,25-(OH)2D3 (1 nM), delayed (3h) stimulation of PAL and GGT appeared. It reached the maximal value after 6h, +37% for PAL and +30% for GGT and persisted again at 8h. Cycloheximide added to incubation medium with steroid inhibited the stimulating effect on PAL only. Actinomycin D suppressed the induction of both enzymes, indicating that the observed actions of 24,25-(OH)2D3 depend on protein synthesis whose responsible mechanisms were different. These protein synthesis inhibitors did not modified enzymatic activities. Physiological significance of these renal effects is to be clarified.

[In vitro effects of 1,25-dihydroxycholecalciferol on alkaline phosphatase and gamma-glutamyltransferase activity in hypophysectomized rats]. / Effets in vitro du 1,25-dihydroxycholecalciferol sur la phosphatase alcaline et la gamma-glutamyltransferase du rein de rat hypophysectomisé.

Effects in vitro of 1,25-dihydroxycholecalciferol (1,25-(OH)2D3) on alkaline phosphatase (PAL), gamma-glutamyltransferase (gamma-GT) and acid phosphatase (PAC) activities were investigated on renal cortex from hypophysectomized rats. In these animals the biosynthesis of 1,25-(OH)2D3 and the specific activities of kidney PAL and gamma-GT were decreased. The course of these effects was determined from 45 min to 8 h. In the presence of 1,25-(OH)2D3 (2 x 10(-6) M) a delayed (5h) but simultaneous stimulation of the three enzymes was observed. It reached a maximum at 6h and disappeared at 8h. The dose-response relation was studied at 6h. In the presence of 1,25-(OH)2D3 (5 x 10(-7) M), the three enzymes were activated. The effect was maximal at 10(-6) M; it was +22% for PAL, +17% and +15% respectively for gamma-GT and PAC compared with controls. Cycloheximide suppressed the induction of PAL but not of gamma-GT activity. The effects of the secosteroid on renal enzymes seems to be a pharmacological more than a physiological one.