THE LIPID-MOBILIZING EFFECT OF SOME PITUITARY GLAND PREPARATIONS

Abstract

ABSTRACT An inhomogeneous human pituitary lipid-mobilizing factor (LMF) different from somatotrophin and adrenocorticotrophin has previously been prepared. The extraction of LMF deprived fat-mobilizing effect of the simultaneously prepared growth hormone. Subcutaneous injection of LMF in rabbits caused hypocalcaemia and hyperglycaemia in addition to the adipokinesis. The preparation procedure which resulted in a homogeneous LMF is reported. When examined for purity by electrophoresis in polyacrylamide gel the material migrated as a single band. The LMF is probably a polypeptide with a molecular weight in the range of 2100 determined by ultracentrifugation. It is a potent adipotrophin in rabbits, and a concentration of 0.001 μg/1.1 ml gave a significant release of nonesterified fatty acids (NEFA) from human subcutaneous fat pads also. No in vitro lipolysis occurred in normal albino mouse or rat fat, whereas concentrations of 0.01–0.1 μg/1.1 ml had lipolytic effect on fat pads from obese yellow mice and from hypophysectomized rats. In addition to the increase of serum NEFA in rabbits, the purified LMF gave a prolonged hyperglycaemia which persisted for nine days following a single subcutaneous injection of 0.5 mg, but it had no influence on the serum calcium level. Evidence is presented suggesting that the lipolytic mechanism for LMF resembles more closely that of adrenocorticotrophin than of somatotrophin. The LMF may be of physiological importance and is perhaps related to a human pituitary diabetogenic adipotrophin. A possible mechanism for the acute and prolonged hyperglycaemia in rabbits is discussed.