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Alendronate decreases urine calcium and supersaturation in genetic hypercalciuric rats.
Kidney Int 1999; 55(1):234-43KI

Abstract

BACKGROUND

The mechanism of excess urine calcium excretion in human idiopathic hypercalciuria (IH) has not been determined but may be secondary to enhanced intestinal calcium absorption, decreased renal calcium reabsorption, and/or enhanced bone demineralization. We have developed a strain of genetic hypercalciuric stone-forming (GHS) rats as an animal model of human IH. When these GHS rats are placed on a low-calcium diet (LCD), urinary calcium (UCa) excretion exceeds dietary calcium intake, suggesting that bone may contribute to the excess UCa excretion. We used the GHS rats to test the hypothesis that bone contributes to the persistent IH when they are fed an LCD by determining if alendronate (Aln), which inhibits bone resorption, would decrease UCa excretion.

METHODS

GHS rats (N = 16) and the parent strain (Ctl, N = 16) were fed 13 g/day of a normal (1.2%) calcium diet (NCD) for seven days and were then switched to a LCD (0. 02%) for seven days. Ctl and GHS rats in each group were then continued on LCD for an additional seven days, with or without injection of Aln (50 micrograms/kg/24 hrs). UCa excretion was measured daily during the last five days of each seven-day period. To determine the effects of Aln on urine supersaturation, the experiment was repeated. All relevant ions were measured, and supersaturation with respect to calcium oxalate and calcium hydrogen phosphate was determined at the end of each period.

RESULTS

UCa was greater in GHS than in Ctl on NCD (7.4 +/- 0.5 mg/24 hrs vs. 1.2 +/- 0.1, GHS vs. Ctl, P < 0.01) and on LCD (3.9 +/- 0.2 mg/24 hrs vs. 0. 7 +/- 0.1, GHS vs. Ctl, P < 0.01). LCD provides 2.6 mg of calcium/24 hrs, indicating that GHS rats are excreting more calcium than they are consuming. On LCD, Aln caused a significant decrease in UCa in GHS rats and brought GHS UCa well below calcium intake. Aln caused a marked decrease in calcium oxalate and calcium hydrogen phosphate supersaturation.

CONCLUSION

Thus, on a LCD, there is a significant contribution of bone calcium to the increased UCa in this model of IH. Aln is effective in decreasing both UCa and supersaturation. The Aln-induced decrease in urine supersaturation should be beneficial in preventing stone formation in humans, if these results, observed in a short-term study using the hypercalciuric stone-forming rat can be confirmed in longer term human studies.

Authors+Show Affiliations

Nephrology Unit, University of Rochester, Rochester, New York, and the University of Chicago, Chicago, Illinois, USA.No affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

9893132

Citation

Bushinsky, D A., et al. "Alendronate Decreases Urine Calcium and Supersaturation in Genetic Hypercalciuric Rats." Kidney International, vol. 55, no. 1, 1999, pp. 234-43.
Bushinsky DA, Neumann KJ, Asplin J, et al. Alendronate decreases urine calcium and supersaturation in genetic hypercalciuric rats. Kidney Int. 1999;55(1):234-43.
Bushinsky, D. A., Neumann, K. J., Asplin, J., & Krieger, N. S. (1999). Alendronate decreases urine calcium and supersaturation in genetic hypercalciuric rats. Kidney International, 55(1), pp. 234-43.
Bushinsky DA, et al. Alendronate Decreases Urine Calcium and Supersaturation in Genetic Hypercalciuric Rats. Kidney Int. 1999;55(1):234-43. PubMed PMID: 9893132.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Alendronate decreases urine calcium and supersaturation in genetic hypercalciuric rats. AU - Bushinsky,D A, AU - Neumann,K J, AU - Asplin,J, AU - Krieger,N S, PY - 1999/1/20/pubmed PY - 1999/1/20/medline PY - 1999/1/20/entrez SP - 234 EP - 43 JF - Kidney international JO - Kidney Int. VL - 55 IS - 1 N2 - BACKGROUND: The mechanism of excess urine calcium excretion in human idiopathic hypercalciuria (IH) has not been determined but may be secondary to enhanced intestinal calcium absorption, decreased renal calcium reabsorption, and/or enhanced bone demineralization. We have developed a strain of genetic hypercalciuric stone-forming (GHS) rats as an animal model of human IH. When these GHS rats are placed on a low-calcium diet (LCD), urinary calcium (UCa) excretion exceeds dietary calcium intake, suggesting that bone may contribute to the excess UCa excretion. We used the GHS rats to test the hypothesis that bone contributes to the persistent IH when they are fed an LCD by determining if alendronate (Aln), which inhibits bone resorption, would decrease UCa excretion. METHODS: GHS rats (N = 16) and the parent strain (Ctl, N = 16) were fed 13 g/day of a normal (1.2%) calcium diet (NCD) for seven days and were then switched to a LCD (0. 02%) for seven days. Ctl and GHS rats in each group were then continued on LCD for an additional seven days, with or without injection of Aln (50 micrograms/kg/24 hrs). UCa excretion was measured daily during the last five days of each seven-day period. To determine the effects of Aln on urine supersaturation, the experiment was repeated. All relevant ions were measured, and supersaturation with respect to calcium oxalate and calcium hydrogen phosphate was determined at the end of each period. RESULTS: UCa was greater in GHS than in Ctl on NCD (7.4 +/- 0.5 mg/24 hrs vs. 1.2 +/- 0.1, GHS vs. Ctl, P < 0.01) and on LCD (3.9 +/- 0.2 mg/24 hrs vs. 0. 7 +/- 0.1, GHS vs. Ctl, P < 0.01). LCD provides 2.6 mg of calcium/24 hrs, indicating that GHS rats are excreting more calcium than they are consuming. On LCD, Aln caused a significant decrease in UCa in GHS rats and brought GHS UCa well below calcium intake. Aln caused a marked decrease in calcium oxalate and calcium hydrogen phosphate supersaturation. CONCLUSION: Thus, on a LCD, there is a significant contribution of bone calcium to the increased UCa in this model of IH. Aln is effective in decreasing both UCa and supersaturation. The Aln-induced decrease in urine supersaturation should be beneficial in preventing stone formation in humans, if these results, observed in a short-term study using the hypercalciuric stone-forming rat can be confirmed in longer term human studies. SN - 0085-2538 UR - https://www.unboundmedicine.com/medline/citation/9893132/Alendronate_decreases_urine_calcium_and_supersaturation_in_genetic_hypercalciuric_rats_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0085-2538(15)30978-9 DB - PRIME DP - Unbound Medicine ER -