THE LIPID-MOBILIZING EFFECT OF SOME PITUITARY GLAND PREPARATIONS

ABSTRACT Clinical observations and endocrinological research have provided evidence of the existence of a specific pituitary regulation of triglycerideolysis in depot fat. A lipid-mobilizing fraction was prepared from deep-frozen human pituitary glands by slightly alkaline extraction followed by acetone precipitation at a pH below the isoelectric point for growth hormone. This crude fraction was purified by Sephadex gel filtration and DEAE-cellulose chromatography. Preparation of this lipid-mobilizing fraction failed when acetone-dried pituitary glands were used. The obtained lipid-mobilizing factor (LMF) had two bands on polyacrylamide gel disc electrophoresis, and the molecular weight was determined to be in the range of 5000. There was loss of lipolytic activity when partly purified LMF was incubated in physiological saline at 37° C. No somatotrophic or thyrotrophic activity was observed in LMF and only traces of prolactin, ACTH- and MSH-like activities. The LMF was lipolytic both in vivo and in vitro on rabbit and human adipose tissue. The effect on mouse and rat was questionable. In rabbits LMF also caused ketonaemia, hyperlipaemia, increased liver fat, decrease of liver glycogen, prolonged hyperglycaemia and decrease of serum calcium and inorganic phosphorus. High doses of LMF induced a hypermetabolic state in the rabbit with marked hypocalcaemia usually accompanied by convulsions and death. It is concluded that the prepared LMF is probably an aggregation of a lipotrophic and a rabbit serum-calcium-lowering factor. The lipotrophic factor may be a specific pituitary 'adipotrophin' or a denaturation product from a previously accepted pituitary hormone. A possible relationship between LMF and a diabetogenic-adipokinetic core of growth hormone is discussed.