Effects pf riboflavin deficiency upon prostaglandin biosynthesis in rat kidney

Abstract The effects of riboflavin deficiency on the activity in vitro of prostaglandin synthetase were determined in rat kidney homogenates. For a period of two to five months, weanling rats were fed either a diet deficient in riboflavin or equal amounts of a diet identical in composition except for the addition of riboflavin at four times the RDA for this vitamin. In further experiments, each group of rats was treated for 10 days with either an inhibitor of cyclooxygenase (flurbiprofen) or buffer. Following sacrifice, prostaglandin biosynthesis in vitro was measured both in the absence and presence of reduced glutathione, and subsequently in the presence of reduced glutathione with and without flurbiprofen. Reaction products were extracted from supernatant solutions with diethylether, and the PGE 2 and PGF 2α formed were measured by radioimmunoassay. Dietary riboflavin deficiency increased biosynthesis rates in vitro of both PGE 2 and PGF 2α in rat renal medulla and papilla. when both control and riboflavin deficient rats were treated with flurbiprofen for a 10 day period, PGE 2 biosynthesis in vitro was markedly inhibited. This inhibition of PGE 2 biosynthesis was partially overcome by the addition of reduced glutath one in vitro . The addition of flurbiprofen in vitro to samples containing reduced glutathione prevented the restoration of PGE 2 biosynthesis by the latter. The rate of prostaglandin biosynthesis in kidney homogenates from riboflavin deficient rats remained higher than that of controls with each experimental manipulation. These data in their entirety suggest a possible role for riboflavin in the regulation of renal prostaglandin biosynthesis in the rat.