Properties of Prostaglandin Synthetase of Rabbit Kidney Medulla

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Abstract
The formation in vitro of prostaglandins [PG] E2, D2 and F2.alpha. from arachidonic acid by rabbit kidney medulla homogenate or microsomal fraction is affected by the composition of the incubation medium. Optimal biosynthesis is obtained in 0.1 M potassium phosphate buffer, with pH of 8.0-8.8. Prostaglandin formation is linear up to arachidonic acid concentration of 30 .mu.M. The initial rate of PGE2 + PGD2 formation is 3-4 times higher than PGF2.alpha.. Reduced glutathione (1 mM) did not affect biosynthesis by medulla homogenate and produced small stimulation of the biosynthesis by microsomal powder. Hydroquinone produced a small stimulation at 0.005 mM, and strong inhibition at 0.1 mM or higher. Addition of bovine serum albumin (0.1%) reduced the microsomal biosynthesis of prostaglandins by approximately 80%. Addition of boiled homogenate or boiled 140,000 .times. g supernatant produced small stimulation of microsomal biosynthesis while 140,000 .times. g supernatant (not boiled) caused small inhibition which was not dose-related. Rabbit kidney prostaglandin-synthetase [EC 1.14.99.1] converts arachidonic acid to PGE2 and PGF2.alpha. in comparable amounts, without apparent need for a cytoplasmic soluble cofactor or specific reducing agents.