Effects of magnesium on renal and intestinal calbindin-D.

The possible effects of magnesium on the vitamin D-dependent renal and intestinal calbindin-D were investigated. In a low magnesium model 70 Wistar rats were allocated to either a normomagnesemic diet (Mg 3.2 g/kg) or a Mg-deficient diet (Mg 0.18 g/kg) for 10 or 24 days. The rats had intraperitoneal injections of 1,25-(OH)2 vitamin D3 0.2 microgram, MgSO4 100 mumol or placebo daily for the last 4 days. In a high magnesium model 60 Wistar rats were allocated to three groups on a normomagnesemic diet supplied with intraperitoneal MgSO4 20 mumol, 100 mumol or placebo daily. Half of the animals in each group were further supplied with intraperitoneal 1,25-(OH)2 vitamin D3 0.2 micrograms daily. The concentrations of intestinal calbindin-D9k increased on the low Mg diet from 1.6 (1.1-2.0) to 2.7 (2.0-2.9) micrograms/mg protein (p < 0.02), but were unchanged in the high Mg groups. Vitamin D treatment raised the levels of calbindin-D9k in the normomagnesemic group (p < 0.01), but not significantly in the low Mg group. Administration of MgSO4 to the low Mg rats normalized the elevated levels of intestinal calbindin-D9k (p < 0.05). The concentrations of renal calbindin-D28k were not changed by the low Mg diet, but were lower in the high Mg group [0.8 (0.6-1.1) micrograms/mg protein] than in the control group [1.5 (1.1-1.8) micrograms/mg protein; p < 0.05]. Animals in the low, high and normal magnesium group showed no differences in plasma concentrations of 1,25-(OH)2 vitamin D.(ABSTRACT TRUNCATED AT 250 WORDS)