The study aimed to compare, by means of stereologic methods, the reactivity of the adrenal cortex of the hamster and the rat to prolonged treatment with 4-aminopyrazolo-(3,4d)pyrimidine (4-APP), a
drug reducing hepatic secretion of plasma
lipoprotein. Adult female hamsters, intact or
cortisone suppressed, were administered i.p. daily with 0.5 mg
4-APP for 5 days while intact female rats received 1 mg of the
drug per dose.
4-APP resulted in a loss of
body weight, with the more profound effect in the hamster. In the rat
4-APP did not change the adrenal gland weight, the volume of the adrenocortical zones, the average volume of adrenocortical cells and the number of parenchymal cells in the gland. Moreover, serum
ACTH and
corticosterone levels in the rat remained unchanged. In the intact hamster
4-APP decreased the adrenal gland weight, the volume of the zona fasciculata and enhanced the serum
cortisol level. In
steroid suppressed hamsters
4-APP lowered the adrenal weight, the volume of fasciculata and reticularis zones, the average volume of the fasciculata cells and the number of parenchymal cells in the gland. These findings may suggest the direct inhibitory effect of low
4-APP doses on the hamster adrenal cortex and clearly demonstrate higher susceptibility of the hamster adrenal cortex, if compared with the rat, to 4-aminopyrazolo-pyrimidine.