Role of the pituitary-adrenocortical system in the stress-induced blood platelet fluctuation.

Abstract

The blood platelet fluctuation observed after surgical interventions and reproduced here in the rat is apparently induced, partly or totally, by the reactions of the pituitary–adrenocortical axis to stress. The stress-induced platelet fluctuation could be the result of a certain adrenal insufficiency, since it can be elicited by simple adrenalectomy and completely prevented in immobilized but otherwise normal rats by hydrocortisone administered solely at the time of the immobilization. The thrombocytosis which occurs from 5 to 8 days after the stress appears to be dependent on the posterior pituitary hormones, since in hypophysectomized rats it could be reproduced only when posterior lobe or whole pituitary extracts were injected or when the posterior lobe had reorganized 26 days after the hypophysectomy. The potassium and sodium concentrations in serum did not seem to exert any influence on the blood platelet level under our conditions.