AJP - Gastrointestinal and Liver Physiology, Vol 242, Issue 2 128-G134, Copyright © 1982 by American Physiological Society
Calcium transport in the ileum of uremic rats
M. Koller and U. Binswanger
Duodenal and ileal calcium transport was studied by 45Ca uptake and
estimation of unidirectional fluxes in vitro in kidney-intact and
5/6-nephrectomized rats. After normal-calcium diet, calcium transport was
impaired by uremia in the duodenum but not in the ileum. However,
5/6-nephrectomized rats on low-calcium diet showed, in concert with
impaired growth, a reduced calcium transport both in duodenum and ileum.
Comparing data after normal- and low-calcium diets, the ileal adaptation to
low-calcium diet was intact in mild renal failure but abolished in severe
uremia (urea less than 100 mg/dl). These results suggest that ileal calcium
transport after normal-calcium diet is mainly passive. Taking into account
reduced food intake as an additional factor, the active ileal calcium
transport after low-calcium diet declines with progressive renal failure
according to decreasing levels of 1,25-dihydroxyvitamin D3. A suspected
enhancement of the distal small intestinal calcium transport by parathyroid
hormone in uremic rats as compensation for proximally impaired absorption
could not be demonstrated.
