THE LIPID-MOBILIZING EFFECT OF SOME PITUITARY GLAND PREPARATIONS

Abstract

Lipid-mobilizing effect has been observed for nearly all the accepted pituitary hormones and for several suggested pituitary 'lipotrophins'. Pituitary hormone preparations are usually not homogeneous, and even a highly purified ACTH (p.ACTH) contains less than 30 per cent pure adrenocorticotrophin. Crude ACTH (c.ACTH) was found to be 250 times more adipokinetic in rabbits than p.ACTH, indicating that this effect was mainly due to impurities. A lipid-mobilizing fraction (LMFr) was precipitated from a human pituitary gland extract before the preparation of growth hormone and crude gonadotrophins, whereby the adipokinetic effect of these preparations in the rabbit became negligible. Removal of LMFr gave an electrophoretically purified growth hormone with reduced molecular weight and an increased somatotrophic potency per unit weight in a radioimmunoassay system. Injection of the lipotrophic preparations into rabbits lowered the serum calcium level, and concentrations below 3 meq./l were observed, often accompanied by convulsions and in some instances by death. It is concluded that the adipokinetic and hypocalcaemic effects of c.ACTH, p.ACTH and the employed human growth hormone preparations in rabbits may be due to contaminations. It is suggested that the LMFr contains a human pituitary lipotrophic factor which may also be responsible for the hypocalcaemia observed in the rabbit.