Effects of cortisol on adrenal phenylethanolamine-N-methyltransferase: antagonistic effects of vitamin D in hypophysectomized rats fed a vitamin D free diet.

The influence of individual or combined administration of vitamin D and hydrocortisone on adrenal phenyl-N-methyltransferase (PNMT) in hypophysectomized rats deprived of vitamin D for 1 month has been studied, as well as adrenal and urinary epinephrine and norepinephrine. Daily administration of vitamin D for 11 days decreased PNMT activity and increased adrenal norepinephrine, whereas adrenal epinephrine remained unaffected. Epinephrine and norepinephrine urinary excretion increased after four and nine injections of vitamin D from the hypophysectomized rats fed a vitamin D free diet for 1 month. Hydrocortisone treatment produced increases in adrenal PNMT and epinephrine as well as in urinary excretion of both monoamines. The effects of individual administration are neutralized when the two products are injected together.