Effect of 1,25-dihydroxyvitamin D3 on plasma concentrations of calcium-binding protein in normal and rachitic (vitamin D-dependent rickets type I) pigs.
An i.v. injection of calcitriol (1,25-(OH)2D3) had no effect within 2.5 h on plasma concentrations of calbindin-D9K (vitamin D-induced calcium-binding protein; CaBP) in hypocalcaemic pigs with inherited vitamin D-dependent rickets type I or in their normocalcaemic siblings or half-siblings. Three days later the plasma concentration of CaBP had doubled in the hypocalcaemic pigs, but was unaltered in the normocalcaemic siblings and half-siblings. Following daily i.v. injections of 1,25-(OH)2D3 for a further 5 days (days 4-8) plasma concentrations of CaBP increased in both the hypocalcaemic (days 4-8) and normocalcaemic (day 8) pigs, the effect being more rapid and greater in the hypocalcaemic 1,25-(OH)2D3-deficient animals. An i.v. injection of 1,25-(OH)2D3 to pure Yucatan pigs also had no effect on plasma concentrations of CaBP within 1.5 h, but in the following 1 h there was some indication of an increase in plasma CaBP levels. In contrast to the normal pigs, insulin-induced hypoglycaemia did not lead to a peak in plasma CaBP concentrations in the hypocalcaemic pigs. There was also no change in the plasma concentrations of 1,25-(OH)2D3 associated with the peak in plasma CaBP following insulin-induced hypoglycaemia in normocalcaemic pigs. These results suggest that changes in plasma concentrations of 1,25-(OH)2D3 are not directly involved in mediating the increase in plasma CaBP which follows hypoglycaemia induced by insulin in normal pigs, although 1,25-(OH)2D3 probably plays a permissive role.
Maunder
E M
EM
Department of Animal Physiology and Nutrition, University of Leeds.
Pillay
A V
AV
Care
A D
AD
D000818:Animals; D002117:Calcitriol / Q000494:pharmacology*; D006996:Hypocalcemia / Q000097:blood; D007003:Hypoglycemia / Q000097:blood; D012279:Rickets / Q000097:blood* / Q000235:genetics; D064030:S100 Calcium Binding Protein G / Q000097:blood*; D013552:Swine
D064030:S100 Calcium Binding Protein G; D002117:Calcitriol