Separate and conjugated in vitro effects of clofibrate and of an organic extract of rat amniotic fluid on microperoxisomes of fetal mouse small intestine.

Separate and conjugated effects of clofibrate and of an organic extract of rat amniotic fluid (RAF) on microperoxisomal response were studied in 15-day-old fetal mouse small intestine in organ culture. At the light-microscopic level, DAB-positive microperoxisomes were not observed in intestinal explants cultured for 48 h with Trowell T8-medium either with (group 1) or without clofibrate (control group) or with the organic extract of RAF alone (group 2). In presence of both clofibrate and the organic extract (group 3), microperoxisomes were readily identified. At the fine structural level, microperoxisomes measured 150-175 nm in diameter in controls and in group 1 and 2. In group 3, numerous microperoxisomes measured up to 0.4 micron in diameter. Total and specific catalase activities exhibited significant decreases when intestinal segments were cultured solely in Trowell T8-medium for 48 h. Addition of clofibrate (1), or of the organic extract of RAF (2), or of both (3) to Trowell T8-medium induced significant increases in total and specific catalase activities: 1.43- and 1.40-fold (1), 2.12- and 2.66-fold (2) and 2.92- and 3.17-fold (3). These results indicate that an organic extract of RAF contains a factor that (a) induces the formation of intestinal microperoxisomes and (b) potentiates the action of clofibrate.