Platelet alpha 2-adrenoceptor and adenylate cyclase in patients with anorexia nervosa and bulimia.

Platelets alpha 2-adrenoceptors were studied in 24 patients with anorexia nervosa shortly after admission to the hospital and after 10% weight gain. Twenty patients with bulimia and 24 healthy age- and sex-matched normal subjects also were studied. Receptor number was significantly increased in patients with bulimia and anorexia nervosa. After 10% weight gain, the receptor number almost normalized in anorexia nervosa patients. Kd values were increased in all patients groups at all times of study. In patients with bulimia or anorexia nervosa, both initially and after weight gain, the maximal effect of prostaglandin E1 (PGE1) on platelet cAMP production was greatly increased, while the half-maximally effective dose was unchanged. Also, the maximal inhibitory effects of epinephrine and clonidine on PGE1-stimulated platelet cAMP production were greater, while the half-maximal dose of both alpha 2-agonists was unchanged. Metabolic and endocrine indicators of starvation were present in both bulimic and anorexia nervosa patients initially. Blood beta-hydroxybutyric acid was elevated, and plasma T3 values and the orthostatic response of plasma norepinephrine (delta NA) were reduced, while cortisol was elevated (only in anorexia nervosa patients). Among these parameters, only delta NA significantly correlated with the actions of PGE1 and epinephrine on cAMP production. In conclusion, the activity of the sympathetic nervous system was reduced in patients with anorexia nervosa and bulimia. This reduction was accompanied by an increased capacity and a decreased affinity of platelet alpha 2-receptors and an increased PGE1 stimulatory and epinephrine inhibitory effects on cAMP production.