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Vitamin D deficiency and renal calcium transport in the rat.
J Clin Invest. 1984 Aug; 74(2):507-13.JCI

Abstract

To examine the role of vitamin D in the renal tubular handling of calcium, clearance studies were performed in three groups of rats: group A rats fed a standard vitamin D-deficient diet (Ca 0.45%, P 0.3%) for 6 wk, were hypocalcemic with secondary hyperparathyroidism; group B rats fed the same diet as in group A but with high calcium (Ca 1.4%) and 20% lactose, were normocalcemic and without secondary hyperparathyroidism; group C rats fed the same diet as in group A but supplemented with 25 U of vitamin D3 orally twice a week, were normocalcemic, vitamin D-replete, and euparathyroid. After thyroparathyroidectomy (TPTX), each rat was infused intravenously with an electrolyte solution that contained a fixed concentration of calcium (0-30 mM) with or without parathyroid hormone (PTH; 0.75 or 2.5 U/h) at a rate of 3 ml/h. Urinary calcium excretion and serum calcium concentrations were measured between 16 and 19 h of the infusion, and the apparent threshold of calcium excretion was determined. The threshold of calcium excretion was lower in vitamin D-deficient TPTX rats (groups A and B) than in vitamin D-replete TPTX rats (group C), and not different between group A and group B. Administration of PTH at a dose of 0.75 U/h increased the threshold of calcium excretion by approximately 0.6 mM in group C, but did not alter the threshold either in group A or group B. Administration of a higher dose of PTH (2.5 U/h) raised the threshold similarly in both group A and group B to the extent comparable with that in group C, when it was given 0.75 U/h of PTH. These results demonstrate that the renal threshold of calcium excretion is decreased in the vitamin D-deficient rats independent of the secondary hyperparathyroidism, and that the higher dose of PTH was necessary to raise the calcium threshold in vitamin D-deficient rats. Thus, present study indicates the presence of dual effects of vitamin D on renal tubular handling of calcium; the one is to facilitate renal calcium reabsorption and the other is to enhance the responsiveness of the tubule to PTH.

Authors

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Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

6086715

Citation

Yamamoto, M, et al. "Vitamin D Deficiency and Renal Calcium Transport in the Rat." The Journal of Clinical Investigation, vol. 74, no. 2, 1984, pp. 507-13.
Yamamoto M, Kawanobe Y, Takahashi H, et al. Vitamin D deficiency and renal calcium transport in the rat. J Clin Invest. 1984;74(2):507-13.
Yamamoto, M., Kawanobe, Y., Takahashi, H., Shimazawa, E., Kimura, S., & Ogata, E. (1984). Vitamin D deficiency and renal calcium transport in the rat. The Journal of Clinical Investigation, 74(2), 507-13.
Yamamoto M, et al. Vitamin D Deficiency and Renal Calcium Transport in the Rat. J Clin Invest. 1984;74(2):507-13. PubMed PMID: 6086715.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Vitamin D deficiency and renal calcium transport in the rat. AU - Yamamoto,M, AU - Kawanobe,Y, AU - Takahashi,H, AU - Shimazawa,E, AU - Kimura,S, AU - Ogata,E, PY - 1984/8/1/pubmed PY - 1984/8/1/medline PY - 1984/8/1/entrez SP - 507 EP - 13 JF - The Journal of clinical investigation JO - J. Clin. Invest. VL - 74 IS - 2 N2 - To examine the role of vitamin D in the renal tubular handling of calcium, clearance studies were performed in three groups of rats: group A rats fed a standard vitamin D-deficient diet (Ca 0.45%, P 0.3%) for 6 wk, were hypocalcemic with secondary hyperparathyroidism; group B rats fed the same diet as in group A but with high calcium (Ca 1.4%) and 20% lactose, were normocalcemic and without secondary hyperparathyroidism; group C rats fed the same diet as in group A but supplemented with 25 U of vitamin D3 orally twice a week, were normocalcemic, vitamin D-replete, and euparathyroid. After thyroparathyroidectomy (TPTX), each rat was infused intravenously with an electrolyte solution that contained a fixed concentration of calcium (0-30 mM) with or without parathyroid hormone (PTH; 0.75 or 2.5 U/h) at a rate of 3 ml/h. Urinary calcium excretion and serum calcium concentrations were measured between 16 and 19 h of the infusion, and the apparent threshold of calcium excretion was determined. The threshold of calcium excretion was lower in vitamin D-deficient TPTX rats (groups A and B) than in vitamin D-replete TPTX rats (group C), and not different between group A and group B. Administration of PTH at a dose of 0.75 U/h increased the threshold of calcium excretion by approximately 0.6 mM in group C, but did not alter the threshold either in group A or group B. Administration of a higher dose of PTH (2.5 U/h) raised the threshold similarly in both group A and group B to the extent comparable with that in group C, when it was given 0.75 U/h of PTH. These results demonstrate that the renal threshold of calcium excretion is decreased in the vitamin D-deficient rats independent of the secondary hyperparathyroidism, and that the higher dose of PTH was necessary to raise the calcium threshold in vitamin D-deficient rats. Thus, present study indicates the presence of dual effects of vitamin D on renal tubular handling of calcium; the one is to facilitate renal calcium reabsorption and the other is to enhance the responsiveness of the tubule to PTH. SN - 0021-9738 UR - https://www.unboundmedicine.com/medline/citation/6086715/Vitamin_D_deficiency_and_renal_calcium_transport_in_the_rat_ L2 - https://doi.org/10.1172/JCI111448 DB - PRIME DP - Unbound Medicine ER -