INHIBITION BY HUMAN SERUM OF THE ADIPOKINETIC EFFECT OF A HUMAN PITUITARY LIPID-MOBILIZING FACTOR (LMF) IN RABBITS

ABSTRACT A lipid-mobilizing factor (LMF) has previously been prepared from human pituitary glands. The LMF was strongly adipokinetic in rabbits. Subcutaneous injection of 0.1 mg gave an increase of serum nonesterified fatty acids (NEFA) in the range of 5 meq./l. Addition of 3 ml normal human serum to LMF reduced its adipokinetic effect. The inhibition of LMF by human serum was specific, since serum from mouse or pig did not reduce the increase of serum NEFA induced by LMF, and human serum had no influence on the adipokinesis given by whale, pig, or synthetic ACTH preparations in rabbits. The human serum inhibition of LMF was located to the gamma G globulin fraction by DEAE-cellulose chromatography. Serum from six children with generalized lipodystrophy had a negligible influence on the adipokinesis in rabbits induced by LMF. Sera from one group of obese patients reduced the adipokinetic effect of LMF as normal control sera, while sera from another group of obese patients made the increase of serum NEFA negligible. It is suggested that the first group of obese patients may be related to Mayer's simple regulatory or 'hyperphagic' type of obesity and the latter to his metabolic type of obesity. Furthermore possible mechanisms for the human serum inhibition of LMF are discussed.