THE LIPID-MOBILIZING EFFECT OF SOME PITUITARY GLAND PREPARATIONS

Abstract

An inhomogeneous human pituitary lipid-mobilizing factor (LMF) different from somatotrophin [STH] and adrenocorticotrophin [ACTH] 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 hypocalcemia and hyperglycemia in addition to the adipokinesis. The preparation procedure which resulted in a homogeneous LMP is reported. When examined for purity by electrophoresis in polyacrylamide gel the material migrated as a single band. The LMP is probably a polypep-tide with a molecular weight in the range of 2100 determined by ul-tracentrifugation. It is a potent adipotrophin in rabbits, and a concentration of 0.001 [mu]g/Ll mlgavea 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 0.001-0.1 [mu]g/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 hyperglycemia which persisted for 9 days following a single subcutaneous injection of 0.5 mg, but it has no influence oh the serum Ca level. Evidence is presented suggesting that the lipolytic mechanism for LMF resembles more closely that of ACTH than of STH. 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 hyperglycemia in rabbits is discussed.