The biosynthesis of prostaglandins by brain tissue in vitro

Brain tissue slices in vitro synthesize both PGF2alpha and PGE2 from endogenous precursors at almost linear rates over the first hour. PGF2alpha biosynthesis predominates except for the cat cerebellum. Catecholamines and adrenochrome greatly activate the formation of PGF2alpha in slices and homogenates. The mechanism appears related to endoperoxide reduction rather than increased availability of precursor. The arachidonic acid for prostaglandin biosynthesis in slices is derived from an intracellular pool that forms immediately after animal death and is sufficient to saturate by cyclooxygenase completely and account for the linear kinetics. Biosynthesis of prostaglandins in vivo must be orders of magnitude less than that found in vitro, unless there is local tissue damaged. PGF2 alpha catabolism by cerebral cortex is very small; however, PGE2 is converted to PGF2alpha by brain slices by a 9-keto reductase activity in significant amounts when added in pharmacological amounts.