Schedl H P, Miller D L, Horst R L, Wilson H D, Natarajan K, Conway T
Am J Physiol. 1986 Apr;250(4 Pt 1):G412-9. doi: 10.1152/ajpgi.1986.250.4.G412.
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.
我们之前发现，与Wistar-Kyoto对照大鼠（WKY）相比，自发性高血压大鼠（SH）的肠道钙转运较低。这些动物喂食相对高钙（1%）饮食，两组血清中1α,25-二羟胆钙化醇[1α,25(OH)₂D₃]的浓度相同。在本实验中，我们测试了SH大鼠钙转运较低是否是由于对1α,25(OH)₂D₃无反应的可能性。我们喂食高钙和低钙饮食，并测量血清1α,25(OH)₂D₃和钙转运。在WKY和SH大鼠中，5周和12周时，血清1α,25(OH)₂D₃均随钙缺乏而增加。在高钙饮食情况下，当在5周龄时对十二指肠进行体外研究，以及在12周龄时对近端和远端小肠进行体内研究时，SH大鼠的钙转运低于WKY大鼠。除了12周龄时远端小肠的体内实验外，SH大鼠的钙转运随钙缺乏而增加，但WKY大鼠未增加。总之，尽管通过喂食高钙饮食使维生素D活性处于基础水平时，SH大鼠的钙转运低于WKY大鼠，但喂食低钙饮食导致1α,25(OH)₂D₃增加时，SH大鼠的钙转运增加。我们得出结论：1）SH大鼠中维生素D调节的介导钙转运成分是完整的，且与高血压无关；2）基础条件下（即非维生素D调节）的介导钙转运在SH大鼠和WKY大鼠中不同，可能与高血压有关。
