Effect of vitamin D depletion on calcium transport by the luminal and basolateral membranes of the proximal and distal nephrons

• Published in: Endocrinology (Philadelphia) Vol. 132; no. 1; p. 115
• Main Authors: Bouhtiauy, I, Lajeunesse, D, Brunette, M G
• Format: Journal Article
• Language: English
• Published: United States 01.01.1993
• Subjects: Adenosine Triphosphate - pharmacology; Animals; Biological Transport; Calcitriol - pharmacology; Calcium - metabolism; Carrier Proteins - metabolism; Cell Membrane - metabolism; Kidney Tubules, Distal - metabolism; Kidney Tubules, Proximal - metabolism; Nephrons - metabolism; Parathyroid Hormone - blood; Rabbits; Sodium-Calcium Exchanger; Vitamin D - blood; Vitamin D Deficiency - metabolism
• ISSN: 0013-7227
• DOI: 10.1210/en.132.1.115

To study the effect of vitamin D on calcium (Ca2+) reabsorption by the kidney, we measured Ca2+ uptake by the basolateral and luminal membranes of proximal and distal tubules obtained from rabbits fed a vitamin D-deficient diet for 3 weeks. Results were compared to those obtained with a group of control animals fed a normal diet. Serum Ca2+ concentrations were comparable in both groups. In the control group, serum PTH, 25-hydroxyvitamin D3, and 1,25-dihydroxyvitamin D3 remained relatively stable. In the vitamin D-deficient animals, serum PTH levels slightly, but not significantly, increased, and the levels of vitamin D metabolites abruptly fell. Vitamin D depletion produced a 40% decrease in ATP-dependent Ca2+ uptake by the basolateral membrane of the distal tubule. There was no change in the activity of the Na+/Ca2+ exchanger. A very significant effect was also observed in the luminal membrane of the distal tubule, where a 50% decrease in Ca2+ uptake was observed after the third week of vitamin depletion. Administration of 0.1 microgram 1,25-dihydroxyvitamin D3 16 and 2 h before death partially reestablished normal uptake. In contrast, no change in Ca2+ uptake could be detected in the basolateral or luminal membranes of the proximal tubule. These observations provide the first evidence of an effect of vitamin D on Ca2+ transport at both the basolateral and luminal membranes of the distal segment of the nephron.