[Metabolism of 25-hydroxyvitamin D3 in the kidney and nuclear receptors of 1,25-dihydroxyvitamin D3 in small intestine mucosa of rats with vitamin B2 deficiency].

Effect of vitamin B2 deficiency on metabolism, reception and biochemical functions of vitamin D was studied in young rats. Deficiency in vitamin B2 was shown to cause a moderate hypocalcemia as well as a decrease in the active transport of calcium in small intestine and in concentration of 25-OH D in blood serum, lowered formation of 24,25 (OH)2D3 in kidney slices and decreasing content of nuclear receptors for 1,25 (OH)2D3 (fre and bound in vivo) in small intestine mucose. After administration of cholecalciferol into the animals deficient in vitamins D and B2 within 24 hrs or 6 days before death restoration of the calcium metabolism parameters was retarded as a result of less distinct stimulation of I-hydroxylase and of low activity of 24-hydroxylase 25-OH D3 in kidney as well as due to a moderate increase in content of bound receptors of 1,25 (OH)2D3 in small intestine mucose and, apparently, because of reduced production of the proteins dependent on vitamin D in the tissue (Ca2+-ATPase and alkaline phosphatase). The data obtained suggest the possible importance in rickets of vitamin B2 deficiency mediated via its influence on metabolism and reception of vitamin D.