Biosynthesis of prostaglandins in microsomes of human skeletal muscle and kidney.

The capacity of human skeletal muscle, renal cortical and renal medullary microsomes to synthesize prostaglandins (PGs) from exogenous precursor was investigated. The microsomal fractions were incubated with [1-14C]-labelled arachidonate ([14C]-AA) in the absence and in the presence of reduced glutathione (GSH). [14C]-PGs formed in the incubates were extracted, separated by thin-layer chromatography and quantified using liquid scintillation spectrometry. [14C]-labelled PGE2, PGF2 alpha and 6-keto-PGF1 alpha were found to be the principal products of microsomal PG formation and appeared in similar relative quantities in the incubates of all three tissues studied. In some incubates of renal cortical and renal medullary microsomes formation of smaller relative amounts of [14C]-PGD2 and thromboxane B2 was also noted. In addition, formation of substantial amounts of a polar, not yet identified compound was frequently observed in all incubates. In the absence of GSH, [14C]-6-keto-PGF1 alpha was the main PG formed by microsomes of all of the three tissues. At the expense of 6-keto-PGF, the addition of GSH resulted in an almost 2-fold stimulation of [14C]-PGF2 alpha formation in the skeletal muscle and renal cortical incubates, whereas in the renal medullary incubates an increase in the relative amounts of [14C]-PGE2 was observed. The PG synthetic capacity was highest in the skeletal muscle and lowest in the renal cortical microsomes. The results demonstrate a considerable capacity of human skeletal muscle and of the renal cortex and renal medulla to synthesize prostacyclin. Furthermore, the data reveal GSH-dependent differences in the expression of PG biosynthesis in these tissues. The GSH-dependent differentiation of PG synthesis may reflect a mechanism of adaptation of local PG production to the physiological processes.