AJP - Gastrointestinal and Liver Physiology, Vol 241, Issue 4 344-G347, Copyright © 1981 by American Physiological Society
Transport of calcium by duodenum of spontaneously hypertensive rat
M. A. Toraason and G. L. Wright
The absorption of calcium by segments of duodenum obtained from
spontaneously hypertensive (SH) rats and normotensive Wistar-Kyoto (WKy)
rats was measured before and after the development of hypertension. The
systolic blood pressure (SBP) of 5-wk-old SH rats (116 +/- 4 Torr) was
significantly elevated above that of age-matched WKy rats (103 +/- 3 Torr)
but was not at a level generally considered to be hypertensive. Values
obtained for calcium transport [ratio of serosal-to-mucosal fluid 45Ca2+
concn (S/M ratio)] from everted duodenal sacs were similar between the two
groups at this age. At 12 wk of age, SH rats exhibited a SBP (153 +/- 4
Torr) well above that of WKy controls (127 +/- 3 Torr), and calcium S/M
ratios for duodenal sacs were significantly greater than the WKy control
values. Similarly, the in vivo uptake of calcium in duodenal segments was
significantly elevated in 12-wk-old SH rats compared with WKy controls. The
administration of vitamin D3 or its metabolite, 25-hydroxycholecalciferol,
had no detectable effect on duodenal transport of calcium in 12-wk-old SH
or WKy rats. By comparison, 1,25-dihydroxycholecalciferol produced a
significant increase in duodenal calcium transport both in vitro and in
vivo in WKy but not in SH rats. The results indicate a distinct abnormality
in the transport of calcium in the duodenum of SH rats, suggesting that the
decrease in duodenal uptake of calcium that normally occurs with maturation
is slow to develop in this rat strain.
