[Mechanism of impairment of calcium metabolism caused by toxin T-2; the role of the vitamin D-dependent endocrine system]. / Mekhanizm narushenii obmena kal'tsiia pri deistvii toksina T-2; rol' éndokrinnoi sistemy vitamina D.

Functions of the vitamin D-dependent endocrine system were studied in rats deprived of the vitamin after administration of T-2 toxin. Impairments of calcium metabolism, alterations in the enzymatic activity related to vitamin D3 bioactivation and receptor binding of the hormonal form 1,25(OH)2D3 were similar both in rats deprived of vitamin D, treated with T-2 toxin within 5 days at a dose of 0.54 mg/kg and in the corresponding controls. At the same time, reduction of the calcium metabolism patterns was retarded in rats obtaining vitamin D3 simultaneously with T-2 toxin. This effect was expressed as a decrease in normalization of 25-OHD concentration in blood, absence of renal I-hydroxylase 25-OHD3 activation, inspite of the higher content of parath hormone in blood and of cAMP in kidney, while concentration of bound 1,25(OH)2D3 receptors was distinctly decreased in tissues-targets in vivo. Thus, the effects of T-2 toxin on the vitamin D-dependent endocrine system were manifested as development of the vitamin, secondary deficiency, as resistance of I-hydroxylase 25OHD3 to regulating effect of parath hormone as well as inhibition of interaction between the complexes 1,25(OH)2D3-receptor and chromatin.