Abstract
The action of prostaglandin E1 on tyrosine hydroxylase activity in adrenal slices of guinea pig was studied. The activity of tyrosine hydroxylase was decreased by the incubation of adrenal slices with prostaglandin E1 at concentrations beyond 2 μg per ml for 2 hours. The activity of tyrosine hydroxylase was stimulated by dibutyryl adenosine 3', 5'-monophosphate in slices of guinea pig adrenal glands. Incubation of adrenal slices with the combination of PGE1 and DBc-AMP led to a tyrosine hydroxylase activity higher than that with PGE1 alone, but not as great as DBc-AMP alone. It was suggested that PGE1 inhibited the enzyme activity independently of the cyclic AMP level. Other prostaglandins such as PGA1 and PGB1 were deficient to the extent that the tyrosine hydroxylase activity was decreased. PGE1 inhibited the enzyme activity much to the same extent seen with protein synthesis inhibitors such as cycloheximide and actinomycin D. However, PGE1 did not influence the incorporation of L-leucine-14C into acid insoluble protein. The studies reported here showed that PGE1 inhibited the synthesis of tyrosine hydroxylase.
