Effect of ascorbic acid on ACTH-induced cyclic AMP formation and steroidogenesis in isolated adrrenal cells of vitamin E-deficient rats

Isolated adrenal cells from Vitamin E-deficient and control rats were prepared by a trypsin digestion method. Cyclic adenosine 3′,5′-monophosphate (cyclic AMP) formation was studied in response to adrenocorticotropin (ACTH) in the presence and absence of ascorbate by measuring the conversion of prelabeled adenosine 5′-triphosphate ¹⁴C]ATP to cyclic ¹⁴C]AMP. Ascorbate (0.5 mM) inhibited ACTH-induced cyclic ¹⁴C]AMP formation in adrenal cells isolated from Vitamin E-deficient rats but had no effect in the control cells. The inhibitory effect of ascorbate on ACTH-induce cyclic AMP formation in Vitamin E-deficient rats decreased as the concentration of ACTH increased. In Vitamin E-deficient rats ascorbate inhibited ACTH-induced cyclic ¹⁴C]AMP formation after 30 min of incubation. There was no further significant accumulation of cyclic ¹⁴C]AMP at 60 min or 120 min although in the absence of ascorbate cyclic ¹⁴C]AMP continued to be formed. The in vitro addition of α-tocopherol reduced the inhibition of ACTH-induced cyclic ¹⁴C]AMP formation by ascorbate in Vitamin E-deficient rats.These studies suggest that α-tocopherol and ascorbate may affect ACTH-induced cyclic AMP formation through interaction with membrane-bound enzyme adenylate cyclase.