Metabolic acidosis enhances 1,25(OH)2D3-induced intestinal absorption of calcium and phosphorus in rats.
The effect of metabolic acidosis on the intestinal absorption of calcium (Ca) and phosphorus (P), plasma vitamin D metabolites and urinary excretion of Ca in adult rats treated with a small dose of 1,25(OH)2D3 were investigated. The rats in the experimental group received 1.8% ammonium chloride (NH4Cl) and a commercial chow, and their pair-fed controls received 0.45% NaCl. Both groups were given subcutaneously 1,25(OH)2D3. Intestinal absorption of Ca and P was measured by gut sac uptake of 45Ca and 32P. In the acidotic rats, duodenal, jejunal and ileal 45Ca uptake as well as jejunal and ileal 32P uptake were significantly increased. Plasma 1,25(OH)2D, 25(OH)D and 24,25(OH)2D were similar in both groups. 1,25(OH)2D3 treatment induced a greater calciuria in acidotic rats and increased their fractional excretion (FE) of Ca. An additional experiment showed increased 45Ca uptake by duodenum at a pH of 7.0 compared to pH 7.4. The present study suggests that NH4Cl-induced metabolic acidosis may enhance the effect of 1,25(OH)2D3 on intestinal absorption of Ca and P in the rat. However, the data from the study cannot exclude the possibility that acidosis may have a direct, vitamin D-independent effect on the intestine.
D000138:Acidosis / Q000378:metabolism*; D000818:Animals; D002117:Calcitriol / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D002132:Calcium Radioisotopes; D005919:Glomerular Filtration Rate; D007408:Intestinal Absorption / Q000187:drug effects*; D007421:Intestine, Small / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D010710:Phosphates / Q000378:metabolism*; D010761:Phosphorus Radioisotopes; D051381:Rats; D011919:Rats, Inbred Strains
D002132:Calcium Radioisotopes; D010710:Phosphates; D010761:Phosphorus Radioisotopes; D002117:Calcitriol; D002118:Calcium