Endocrinology, Vol 104, 1266-1269, Copyright © 1979 by Endocrine Society
The cholesterol side chain cleavage system of the rat adrenal cortex and its relationship to the circadian rhythm
AC Brownie, RE Kramer and S Gallant
The adrenal mitochondrial cytochrome P450 systems were examined at the low
and high points of the circadian rhythm in female rats maintained on a
light cycle from 0600--1800 h. The rate of association of cholesterol with
the cholesterol side chain cleavage form of cytochorme P450 (P450scc) was
measured by light absorption spectrometry. Cholesterol binding to P450scc
was as high in rats killed at the beginning of the dark period as it was in
stressed rats at the beginning of the light period. Stressing rats at the
beginning of the dark period did not result in a further increase in the
rate of cholesterol association with P450scc despite a further increase in
serum corticosterone levels. This suggests that other reactions of
cholesterol metabolism in the adrenal cortex are contributing in a
significant way to the increased rate of corticosteroidogenesis seen in the
stressed animals.
