Different effects of cycloheximide and chloramphenicol on corticosterone production by isolated rat adrenal cells

The distribution and fate of 14C-chloramphenicol in the new-born pig

The distribution of 14C-chloramphenicol has been studied in new-born pigs with the aid of whole-body autoradiography. In the lung, liver, adrenal cortex, kidney, myocardium, pancreas, thyroid, spleen and skeletal muscle the amounts of radioactivity were higher than that of the blood short time after injection and remained higher than the blood up to 8 hrs. After 4 and 8 hrs the brain concentration of 14C was also higher than that of the blood. In the bone marrow, however, the concentration did not reach that of the blood during the whole experiment. In the organs more than 90% of the radioactivity was represented by chloramphenicol: the excretory organs, thyroids, and adrenals being exceptions.

Effects of cholesterol, hydroxycholesterols and calcium on pregnenolone production rates in mitochondrial fractions from rat testes

The in vitro regulation of the mitochondrial conversion of cholesterol to pregnenolone in rat testis tissue has been further investigated. Pregnenolone production rates by isolated mitochondrial fractions could be stimulated by the addition of cholesterol. The stimulation was always highest in mitochondria isolated from lutropin-treated testes relative to control and cycloheximide treated testes. Addition 20- or 25-hydroxycholesterol resulted in a greater stimulation of pregnenolone production rates and these rates were unaffected by prior treatment with cycloheximide. When both cholesterol and 20- or 25-hydroxycholesterol were present in the incubation medium, pregnenolone production rates were mainly influenced by the hydroxycholesterol, even in the presence of a ten-fold excess of cholesterol. Ca2+ in vitro stimulated pregnenolone production rates from endogenous cholesterol as well as from added cholesterol. However, pregnenolone production rates in the presence of hydroxycholesterol were not influence by the addition of Ca2+ in vitro.