Alteration of Normal Development of Drug Metabolism by Injection of Growth Hormone

GROWTH hormone (STH) may affect the normal development of the rat hepatic microsomal drug-metabolizing enzyme system, for there is a normal postnatal, age-related increase in activity of this system1,2. A relation between pituitary hormones and liver drug metabolism was suggested by the observation that the normal postnatal development of hexobarbital, aminopyrine and p-nitrobenzoic acid metabolism was prevented in young male rats which had high levels of STH (ref. 2) from a pituitary mammotropic tumour (MtT–F4) (ref. 3). In adult rats injected with STH a decrease in hepatic microsomal drug metabolism was observed4. This report demonstrates a reduction in the level and rate of increase with age of aminopyrine and ethylmorphine metabolism by liver from STH injected young rats and thus suggests STH as an endogenous agent responsible for the observed postnatal development pattern of this metabolism.