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- Title
Increased urinary saturation and kidney calcium content in genetic hypercalciuric rats.
- Authors
Bushinsky, David A.; Kim, Mark; Sessler, Nelson E.; Nakagawa, Yasushi; Coe, Fredric L.
- Abstract
We have established a colony of genetic hypercalciuric (IH) rats as a model of idiopathic hypercalciuria in humans. To test the hypothesis that hypercalciuria can cause crystallization in kidneys through increased supersaturation, in the absence of confounding effects of diet and whatever complex inhibitor disorders underlay stone disease, we fed males and females of the 21st generation of IH rats 13 g per day of a low calcium (LCD, 0.02% Ca), followed by a normal calcium (NCD, 0.6% Ca) and then a high calcium (HCD, 1.2% Ca) diet, each for seven days. During the last 24 hours of each period complete urine collections were obtained and analyzed for all substances known to affect urinary calcium oxalate (CaOx) and brushite (CaHPO₄) supersaturation. Relative supersaturation with respect to the solid phases of CaOx and CaHPO₄ were then calculated. Compared to same gender controls (Ctl) urine calcium excretion was higher in the female IH rats on all diets and in the male IH rats on NCD and HCD. The female and male IH rats on NCD and HCD were supersaturated with respect to CaOx; however, the male and female Ctl were supersaturated with respect CaOx only on HCD. The female IH rats on NCD and HCD and the male IH rats on NCD were supersaturated with respect to CaHPO₄ however, neither the male nor female Ctl rats were supersaturated with respect to CaHPO₄ on any diet. On NCD and HCD urine supersaturation with respect to CaHPO₄ by females exceeded that of males. Kidney calcium content was greater in the female IH rat (120 ± 13 μg/g kidney) than in any other group (male IH, 68 ± 6; female Ctl, 74 ± 4 and male Ctl 62 ± 4; all P < 0.01 vs. female IH) and calcium content was correlated with CaHPO₄ but not CaOx. Thus, female IH rats have greater urinary CaHPO₄ supersaturation than Ctl rats or male IH rats, and these female IH rats have a greater kidney calcium content. The increased urinary calcium concentration in this inbred strain of hypercalciuric rats leads to urinary supersaturation, leading to calcium precipitation within the kidney.
- Subjects
KIDNEYS; CALCIUM; URINE; HYPERCALCIUREA; CALCIUM metabolism disorders; LABORATORY rats
- Publication
Kidney International, 1994, Vol 45, Issue 1, p58
- ISSN
0085-2538
- Publication type
Article
- DOI
10.1038/ki.1994.7