PRESENCE OF 15-HYDROXY PROSTAGLANDIN DEHYDROGENASE, PROSTAGLANDIN-DELTA13-REDUCTASE AND PROSTAGLANDIN E-9-KETO ALPHA-REDUCTASE IN FROG SPINAL-CORD

Metabolism of prostaglandin E1 (PGE1) and PGF1.alpha. was studied in the frog spinal cord, using a hemisected preparation in vitro and tissue homogenates (whole homogenate and tissue fractions). In intact tissue, PGE1 was converted to 3 metabolites (I-III), whereas only 2 metabolites (II and III) were detected in experiments with PGF1.alpha.. Work with tissue homogenates confirmed that PG transformation is enzymatic, and endproducts were identified as PGF1.alpha. metabolite (metabolite I), 15-keto metabolite (metabolite II) and 15-keto-13,14-dihydro metabolite (metabolite III). The 15-keto-13,14-dihydro metabolite was formed via the 15-keto metabolite which is consistent with findings elsewhere. These results establish the presence in the frog spinal cord of 2 pathways for PG metabolism, 1 consisting of the 15-hydroxy prostaglandin dehydrogenase (15-PGDH) and the prostaglandin-.DELTA.13-reductase (13-PGR), the other of the prostaglandin E 9-keto(.alpha.)-reductase (9K-PGR). 9K-PGR is regarded as an inactivating enzyme, because amphibian spinal neurons are less responsive to PGF1.alpha. than to PGE1. In the intact or in the homogenized tissue, PGE1 is metabolized more efficiently by the 15-PGDH/13-PGR than by the 9K-PGR route. The 15-PGDH metabolizes PGE1 more readily than PGF1.alpha.. The present findings, and previous demonstration of active PG synthesis in the tissue and the potent actions of exogenous PG, strongly suggest that the PG play an important role in the function of neurons in the frog spinal cord.