Impaired intestinal absorption of vitamin D3 in azotemic rats.

Changes in vitamin D metabolism and their effect on calcium and bone metabolism in uremia have been extensively studied. However, the possible effect of uremia on intestinal absorption of vitamin D has not been investigated. We determined the rate of intestinal absorption of vitamin D3 in uremic and normal rats using a well-defined in vivo perfusion technique under identical experimental conditions. The rate of jejunal absorption of vitamin D3 in uremic animals (5.09 +/- 1.87 pmol/100 cm/h) was significantly less (p less than 0.001) than that found in the control animals (11.5 +/- 1.6 pmol/100 cm/h). While the underlying mechanism(s) of the observed reduction in vitamin D absorption in uremia is not known, its recognition adds another dimension to the previously recognized abnormalities of vitamin D metabolism in uremia.