Disturbance in the pressor and chronotropic effects of epinephrine and norepinephrine as well as in the function and structure of adrenal cortex induced by O,P'-DDt

ABSTRACT

The effect of O, P'-DDT on the cardiovascular effects of catecholamines and on the function and structure of the adrenal cortex was evaluated in rabbits. Administration of 50 mg/kg/day O, P'-DDT orally to rabbits for two and three weeks significantly decreased the mean arterial blood pressure and heart rate. The mean percentage increase in the pressor and chronotropic effects of intravenously injected graded doses of epinephrine and norepinephrine were markedly decreased in vagotomized rabbits pretreated with 50 mg/kg/day O, P'-DDT orally for two and three weeks. These effects of O,P'-DDT were more marked after three weeks than after two weeks of its administration. The administration of cortisol, but not aldosterone was found to be capable of potentiating the pressor and chronotropic effects of intravenously injected graded doses of catecholamines in vagotomized rabbits pretreated with O,P'-DDT. Treatment of rabbits with 50 mg/kg/day O,P'-DDT orally for one week produced insignificant change in the plasma cortisol level, significant decrease in the plasma aldosterone and sodium levels and significant increase in the plasma potassium level. The plasma cortisol, aldosterone and sodium levels were markedly decreased, while the plasma potassium level was markedly increased after administration of the same dose of O, P'-DDT to rabbits for two and three weeks. Also, the intensity of these effects of O, P'-DDT was directly related to the duration of administration. The administration of ACTH to rabbits pretreated with 50 mg/kg/day O,P'-DDT orally for three weeks, failed to alter the effects of O,P'- DDT on the plasma cortisol aldosterone and electrolyte levels. The histopathological changes were studied and indicated that O,P'-DDT has a definite effect on the adrenal cortex of the rabbits ranging from outer zonal fatty change to diffuse fatty change with hemorrhage and foci of necrosis depending on the duration of administration. It is concluded that O,P' DDT has the ability to produce a disturbance in the cardiovascular effects of catecholamines and a direct impairment in the function and structure of the adrenal cortex