AJP - Gastrointestinal and Liver Physiology, Vol 238, Issue 5 424-G428, Copyright © 1980 by American Physiological Society
Calcium ATPase and intestinal calcium transport in uremic rats
H. Schiffl and U. Binswanger
Calcium ATPase, an enzyme involved in intestinal calcium transport, was
measured in homogenates of duodenal mucosal scrapings of normal and uremic
rats. The effects of calcium deprivation and treatment with 1
alpha,25-dihydroxycholecalciferol [1,25-(OH)2D3] were investigated as well.
Uremia decreased the enzyme activity and impaired the rise after calcium
deprivation as observed in intact rats. The 1,25-(OH)2D3 treatment
increased the enzyme activity in uremic animals and resulted in an
identical response to calcium deprivation as observed in intact rats;
parathyroidectomy abolished this effect. A striking correlation between
everted duodenal gut sac calcium transport and calcium ATPase activity
could be demonstrated for all groups of rats studied. It is concluded that
the calcium ATPase activity is linked to the production of 1,25-(OH)2D3 as
well as to an additional factor, probably parathyroid hormone. The close
relationship between enzyme activity and in vitro calcium transport, even
during constant physiological supplementation with 1,25-(OH)2D3, suggests
an autonomous role of the calcium ATPase activity for mediation of calcium
transport in the duodenum in addition to the well-known mechanisms related
to vitamin D and its metabolites.
