ISSN:
1432-0827
Keywords:
SHR-WKY rats
;
Calcium
;
Calcitriol
;
Intestine
;
Calbindin
;
Alkaline phosphatase
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
,
Physics
Notes:
Summary the response pattern of plasma calcitriol level and related intestinal adaptation to short-term moderate calcium (Ca) restriction was examined in adolescent male, spontaneously hypertensive rats (SHR) and normotensive WKY control rats. Twelve-week-old SHR and WKY fed a low (0.1%) Ca diet for 3, 6, or 12 days were compared with rats of either strain fed a normal (1.0%) Ca diet. Plasma calcitriol response was measured and duodenal adaptation to Ca restriction was investigated by evaluating active Ca transport, calbindin-D9K (CaBP9K) protein, CaBP9k mRNA, and alkaline phosphatase activity (ALP). Under the normal Ca diet, no significant difference between strains was observed for all five parameters. In response to the low Ca diet, the SHR and WKY showed a similar increase (nearly 50%) in plasma calcitrol, starting at day 3 of this diet. However, only the WKY displayed the expected duodenal adaptation: active Ca transport increased at day 6 and CaBP9K as well as ALP increased at day 3 of the low Ca diet. The stimulation of the latter three parameters was maintained until day 12 of Ca restriction. Moreover, CaBP9K mRNA was increased in WKY after 3 days of Ca restriction. In contrast, the SHR had either no or only a minor increase of duodenal parameters in response to Ca restriction. Finally, a significant and positive correlation between Ca transport and plasma calcitriol and between Ca transport and CaBP9K was found in WKY but not in SHR. In conclusion, this study showed that the adolescent SHR was able to increase calcitriol production but unlike the WKY, it failed to fully adapt at the intestinal target level during a 12-day low Ca diet. Thus, our results provide further evidence for an impairment of the vitamin D endocrine system in adolescent SHR as demonstrated by an abnormal intestinal responsiveness to circulating calcitriol during moderate, short-term Ca restriction.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00296657
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