AJP - Gastrointestinal and Liver Physiology, Vol 250, Issue 4 412-G419, Copyright © 1986 by American Physiological Society
Intestinal calcium transport in the spontaneously hypertensive rat: response to calcium depletion
H. P. Schedl, D. L. Miller, R. L. Horst, H. D. Wilson, K. Natarajan and T. Conway
We previously found intestinal Ca2+ transport to be lower in the
spontaneously hypertensive (SH) as compared with the Wistar-Kyoto control
(WKY) rat. These animals were fed a relatively high (1%) Ca2+ diet, and the
concentration of 1 alpha,25-dihydroxycholecalciferol [1 alpha,25(OH)2D3] in
serum was the same in both groups. In the present experiment we tested the
possibility that the lower Ca2+ transport in the SH rat was the result of
unresponsiveness to 1 alpha,25(OH)2D3. We fed diets high and low in Ca2+
and measured serum 1 alpha,25(OH)2D3 and Ca2+ transport. Serum 1
alpha,25(OH)2D3 increased in response to Ca2+ depletion at both 5 and 12 wk
in both the WKY and SH rat. With high-Ca2+ diet, Ca2+ transport was lower
in SH than in WKY when studied 1) in vitro in duodenum at 5 wk of age, and
2) in vivo in proximal and distal small intestine at 12 wk of age. Ca2+
transport increased in SH in response to Ca2+ depletion, but not in WKY,
except in distal small intestine in vivo at 12 wk. In summary, although
Ca2+ transport is lower in the SH as compared with the WKY rat when vitamin
D activity is basal through feeding a high-Ca2+ diet, Ca2+ transport
increases in the SH rat in response to the increase in 1 alpha,25(OH)2D3
produced by feeding a low-Ca2+ diet. We conclude that 1) the vitamin
D-regulated component of mediated Ca2+ transport is intact in the SH rat
and is unrelated to hypertension, and 2) mediated Ca2+ transport under
basal conditions, i.e., nonvitamin D-regulated, differs in the SH and WKY
rats and may be related to hypertension.
