Kidney Week

Abstract: FR-PO310

Magnesium Decreases Urine Supersaturation but Not Calcium Oxalate Stone Formation in Genetic Hypercalciuric Stone-Forming Rats

Session Information

• Bone and Mineral Metabolism: Basic
  November 03, 2023 | Location: Exhibit Hall, Pennsylvania Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Bone and Mineral Metabolism

• 501 Bone and Mineral Metabolism: Basic

Authors

• Li, Qiaoli, Thomas Jefferson University, Philadelphia, Pennsylvania, United States

Qiaoli Li,

• Krieger, Nancy S., University of Rochester, Rochester, New York, United States

Nancy S. Krieger,

• Yang, Lee, Laboratory Corporation of America Holdings, Itasca, Illinois, United States

Lee Yang,

• Asplin, John R., Laboratory Corporation of America Holdings, Itasca, Illinois, United States

John R. Asplin,

• Bushinsky, David A., University of Rochester, Rochester, New York, United States

David A. Bushinsky,

Background

This study assessed the effect of oral magnesium on urine parameters and stone formation in a genetic hypercalciuric stone-forming (GHS) rat model of human idiopathic hypercalciuria.

Methods

When fed the oxalate precursor, hydroxyproline, every GHS rat develops calcium oxalate stones. These rats, fed a normal calcium (Ca) and phosphorus (P) diet with hydroxyproline, were divided into three groups of ten rats per group: control diet with 4.0 g/kg MgO, low MgO diet (0.5 g/kg), and high MgO diet (8.0 g/kg). At baseline and at 6 weeks, twenty-four-hour urines were collected, and urine chemistry and supersaturation were determined. Stone formation was quantified.

Results

After six weeks those fed the low Mg diet had a significant reduction in urinary Mg and those fed the high Mg diet had a significant increase in urinary Mg compared to those fed the control diet. Dietary Mg did not alter urine Ca excretion while the low Mg diet led to a significant fall in urinary Ox. The low Mg diet increased urinary NH₄ and decreased urinary citrate while the high Mg diet reduced urinary NH₄ and increased urinary citrate. Urine supersaturation with respect to calcium oxalate was significantly increased with low Mg, whereas urine supersaturation was significantly decreased with high Mg. Neither a low nor high Mg diet altered kidney stone formation.

Conclusion

In genetic hypercalciuric stone-forming rats, dietary Mg significantly altered urinary CaOx supersaturation; a low Mg diet increased and a high Mg diet decreased CaOx supersaturation. There was no effect of dietary Mg on stone formation within 6 weeks of treatment.

Urine supersaturation (SS) of CaOx was differentially regulated by Mg. Results are mean ± SEM. ^*P < 0.05 versus CTL; ^oP < 0.05 versus low Mg.

Funding

• NIDDK Support