Calcium and vitamin D metabolism in spontaneously hypertensive rats.
We have studied the effect of dietary vitamin D restriction on serum levels of vitamin D metabolites in spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY). Both WKY and SHR were fed a vitamin D-deficient or a vitamin D-supplemented diet beginning at 4 wk of age. In vitamin D-supplemented animals, the serum 1,25-dihydroxycholecalciferol [1,25(OH)2D3] concentration of WKY (55.4 +/- 6.6 pg/ml, n = 5) was similar to the level of SHR (46.3 +/- 5.9 pg/ml, n = 5). Plasma calcium concentration was not different between WKY and SHR. In animals fed a vitamin D-deficient diet, the serum concentration of 1,25-(OH)2D3 of SHR (23.0 +/- 1.3 pg/ml, n = 5) was significantly lower than that of WKY (67.6 +/- 4.6 pg/ml, n = 5, P less than 0.01). Plasma 25-hydroxycholecalciferol level was markedly decreased in both WKY (3.6 +/- 0.5 ng/ml, n = 7) and SHR (2.8 +/- 0.4 ng/ml). The SHR, but not the WKY, developed hypocalcemia (WKY, 9.68 mg/dl; SHR, 6.70 mg/dl). Despite hypocalcemia, fasting urinary Ca2+ excretion of SHR exceeded that of WKY. We conclude that the lower 1,25(OH)2D3 level in SHR fed a vitamin D-deficient diet may be due to a defect in the synthesis of 1,25(OH)2D3. The low level of 1,25(OH)2D3 is associated with renal wasting of calcium and hypocalcemia in SHR.
Hsu
C H
CH
Department of Internal Medicine, University of Michigan Medical School, Ann Arbor 48109.
Yang
C S
CS
Patel
S R
SR
Stevens
M G
MG
D000818:Animals; D002117:Calcitriol / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D005919:Glomerular Filtration Rate; D006863:Hydrogen-Ion Concentration; D006973:Hypertension / Q000378:metabolism*; D007408:Intestinal Absorption; D008297:Male; D008657:Metabolic Clearance Rate; D010758:Phosphorus / Q000097:blood / Q000378:metabolism; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D014807:Vitamin D / Q000097:blood*; D014808:Vitamin D Deficiency / Q000097:blood
D014807:Vitamin D; D010758:Phosphorus; D002117:Calcitriol; D002118:Calcium