EFFECT OF HYPOPHYSECTOMY ON TISSUE MAO ACTIVITY

Abstract

To an endocrinologist, the term “stress” signifies an occurrence that results in the stimulation of the hypothalamo-pituitary-adrenal axis. The possible role of catecholamines in this system as a link between neuronal activity and the release of the corticotrophin releasing factor (CRF) into the hypophyseal portal vessels has been studied. Steroid hormones might influence the catabolism of biogenic monoamines by affecting the activity of the enzyme monoamine oxidase (MAO). It has been found that adrenalectomy in the rat caused an increase in cardiac MAO activity and that this effect could be prevented by cortisol. The normal cardiac MAO activity in rats with regenerated adrenal glands showed that the effect of adrenalectomy was because of the absence of the adrenal cortex and not the medulla. Progesterone has been found to stimulate tissue MAO activity and oestrogens to decrease it, the extent of the effect being dependent on the substrate used. In the adrenal gland, MAO activity was not only demonstrated in the catecholamine rich medulla but also in the adrenal cortex. The ratio of the enzyme activity in the adrenal cortex and in the adrenal medulla is species dependent.