Vitamin D increases expression of the tyrosine hydroxylase gene in adrenal medullary cells.
We examined expression of the 1,25-dihydroxyvitamin D3 [1,25-(OH)2 D3] receptors in chromaffin cells of the adrenal medulla and the effects of 1,25(OH)2 D3 on expression of the tyrosine hydroxylase (TH) gene. Accumulation of 1,25(OH)2 D3 in the nuclei of adrenal medullary cells, but not in the adrenal cortex, was observed in mice intravenously injected with radioactively labeled hormone. 1,25(OH)2 D3 produced concentration-dependent increases in the TH mRNA levels in cultured bovine adrenal medullary cells (BAMC). The maximal increases (2-3-fold) occurred at 10(-8) M 1,25(OH)2 D3. Combined treatment with 1,25(OH)2 D3 and 20 microM nicotine had no additive effect on TH mRNA levels suggesting that transsynaptic (nicotinic) and vitamin D (hormonal) stimulation of TH gene expression are mediated through converging mechanisms. Induction of TH mRNA by 1,25(OH)2 D3 was not affected by calcium antagonist TMB-8. By increasing expression of the rate limiting enzyme in the catecholamine biosynthetic pathway, 1,25-(OH)2 D3 may participate in the regulation of catecholamine production in adrenal chromaffin cells. This regulation provides mechanisms through which 1,25(OH)2 D3 may control response and adaptation to stress.