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Increased dietary oxalate does not increase urinary calcium oxalate saturation in hypercalciuric rats.
Kidney Int 1999; 55(2):602-12KI

Abstract

BACKGROUND

Human calcium oxalate (CaOx) nephrolithiasis may occur if urine is supersaturated with respect to the solid-phase CaOx. In these patients, dietary oxalate is often restricted to reduce its absorption and subsequent excretion in an effort to lower supersaturation and to decrease stone formation. However, dietary oxalate also binds intestinal calcium which lowers calcium absorption and excretion. The effect of increasing dietary oxalate on urinary CaOx supersaturation is difficult to predict.

METHODS

To determine the effect of dietary oxalate intake on urinary supersaturation with respect to CaOx and brushite (CaHPO4), we fed 36th and 37th generation genetic hypercalciuric rats a normal Ca diet (1.2% Ca) alone or with sodium oxalate added at 0.5%, 1.0%, or 2.0% for a total of 18 weeks. We measured urinary ion excretion and calculated supersaturation with respect to the CaOx and CaHPO4 solid phases and determined the type of stones formed.

RESULTS

Increasing dietary oxalate from 0% to 2.0% significantly increased urinary oxalate and decreased urinary calcium excretion, the latter presumably due to increased dietary oxalate-binding intestinal calcium. Increasing dietary oxalate from 0% to 2.0% decreased CaOx supersaturation due to the decrease in urinary calcium offsetting the increase in urinary oxalate and the decreased CaHPO4 supersaturation. Each rat in each group formed stones. Scanning electron microscopy revealed discrete stones and not nephrocalcinosis. X-ray and electron diffraction and x-ray microanalysis revealed that the stones were composed of calcium and phosphate; there were no CaOx stones.

CONCLUSION

Thus, increasing dietary oxalate led to a decrease in CaOx and CaHPO4 supersaturation and did not alter the universal stone formation found in these rats, nor the type of stones formed. These results suggest the necessity for human studies aimed at determining the role, if any, of limiting oxalate intake to prevent recurrence of CaOx nephrolithiasis.

Authors+Show Affiliations

Nephrology Unit, University of Rochester, New York, USA. David_Bushinsky@urmc.rochester.eduNo affiliation info availableNo affiliation info availableNo 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

9987084

Citation

Bushinsky, D A., et al. "Increased Dietary Oxalate Does Not Increase Urinary Calcium Oxalate Saturation in Hypercalciuric Rats." Kidney International, vol. 55, no. 2, 1999, pp. 602-12.
Bushinsky DA, Bashir MA, Riordon DR, et al. Increased dietary oxalate does not increase urinary calcium oxalate saturation in hypercalciuric rats. Kidney Int. 1999;55(2):602-12.
Bushinsky, D. A., Bashir, M. A., Riordon, D. R., Nakagawa, Y., Coe, F. L., & Grynpas, M. D. (1999). Increased dietary oxalate does not increase urinary calcium oxalate saturation in hypercalciuric rats. Kidney International, 55(2), pp. 602-12.
Bushinsky DA, et al. Increased Dietary Oxalate Does Not Increase Urinary Calcium Oxalate Saturation in Hypercalciuric Rats. Kidney Int. 1999;55(2):602-12. PubMed PMID: 9987084.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Increased dietary oxalate does not increase urinary calcium oxalate saturation in hypercalciuric rats. AU - Bushinsky,D A, AU - Bashir,M A, AU - Riordon,D R, AU - Nakagawa,Y, AU - Coe,F L, AU - Grynpas,M D, PY - 1999/2/13/pubmed PY - 1999/2/13/medline PY - 1999/2/13/entrez SP - 602 EP - 12 JF - Kidney international JO - Kidney Int. VL - 55 IS - 2 N2 - BACKGROUND: Human calcium oxalate (CaOx) nephrolithiasis may occur if urine is supersaturated with respect to the solid-phase CaOx. In these patients, dietary oxalate is often restricted to reduce its absorption and subsequent excretion in an effort to lower supersaturation and to decrease stone formation. However, dietary oxalate also binds intestinal calcium which lowers calcium absorption and excretion. The effect of increasing dietary oxalate on urinary CaOx supersaturation is difficult to predict. METHODS: To determine the effect of dietary oxalate intake on urinary supersaturation with respect to CaOx and brushite (CaHPO4), we fed 36th and 37th generation genetic hypercalciuric rats a normal Ca diet (1.2% Ca) alone or with sodium oxalate added at 0.5%, 1.0%, or 2.0% for a total of 18 weeks. We measured urinary ion excretion and calculated supersaturation with respect to the CaOx and CaHPO4 solid phases and determined the type of stones formed. RESULTS: Increasing dietary oxalate from 0% to 2.0% significantly increased urinary oxalate and decreased urinary calcium excretion, the latter presumably due to increased dietary oxalate-binding intestinal calcium. Increasing dietary oxalate from 0% to 2.0% decreased CaOx supersaturation due to the decrease in urinary calcium offsetting the increase in urinary oxalate and the decreased CaHPO4 supersaturation. Each rat in each group formed stones. Scanning electron microscopy revealed discrete stones and not nephrocalcinosis. X-ray and electron diffraction and x-ray microanalysis revealed that the stones were composed of calcium and phosphate; there were no CaOx stones. CONCLUSION: Thus, increasing dietary oxalate led to a decrease in CaOx and CaHPO4 supersaturation and did not alter the universal stone formation found in these rats, nor the type of stones formed. These results suggest the necessity for human studies aimed at determining the role, if any, of limiting oxalate intake to prevent recurrence of CaOx nephrolithiasis. SN - 0085-2538 UR - https://www.unboundmedicine.com/medline/citation/9987084/Increased_dietary_oxalate_does_not_increase_urinary_calcium_oxalate_saturation_in_hypercalciuric_rats_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0085-2538(15)46004-1 DB - PRIME DP - Unbound Medicine ER -