ABSTRACT
A comparison has been made of some physicochemical and metabolic characteristics of a human growth hormone preparation with somatotrophic and adipokinetic-diabetogenic activity (r.HGH), of a purified r.HGH with potent somatotrophic effect but negligible adipokinetic-diabetogenic effect in the fed animal (t.STH), and a human pituitary-hyperglycaemic and lipid-mobilizing factor (LMF) which was prepared from the crude pituitary extract prior to the preparation of t.STH and was without somatotrophic activity.
The t.STH was separated into two bands on polyacrylamide gel electrophoresis, and an additional band was observed for r.HGH in the area of the single band obtained for LMF. The r.HGH, t.STH, and LMF preparations had maximum optical absorption at 278 mμ up to pH 10. At a more alkaline pH the absorption spectrum of t.STH was unchanged, whereas an additional absorption peak at 290 mμ appeared for r.HGH and LMF. Tentative molecular weights determined by Sephadex gel filtration were in the range of 25 000 for r.HGH, 21 000 for t.STH, and 5500 for LMF.
The t.STH had a significantly higher growth promoting activity in the tibia test than r.HGH. LMF had no such activity in doses of 1 mg. The adipokinetic effect in fed rabbits was strong for LMF and r.HGH, but negligible for t.STH, which, however, caused an increase of nonesterified fatty acids in animals deprived of food. The in vitro lipolytic effect on human fat, obtained from fasting females, for LMF, r.HGH, and t.STH was on a per weight basis in the ratio of 100:10:1, respectively. In rabbits daily injections of r.HGH and LMF, but not t.STH, induced a hyperglycaemia which continued for 9 and 23 days respectively. Rabbits given daily injections of r.HGH and LMF got a diabetic response of blood glucose after injection of adrenalin and prednisone, although an increased sensitivity to insulin. In contrast to this, a single injection of LMF gave a decreased sensitivity to insulin in the rabbit. Rabbits treated with t.STH behaved as untreated controls.
Preparative ultracentrifugation of r.HGH dissolved in physiological saline gave a precipitate with the characteristics of t.STH, and a supernatant with potent hyperglycaemic-adipokinetic effect in rabbits. It was furthermore possible to subdivide r.HGH into t.STH and an adipotrophic component by acetone precipitation and Sephadex gel filtration.
It is discussed whether the r.HGH is an aggregation product of t.STH and a hyperglycaemic-adipokinetic agent, or whether the r.HGH is original and made up of these two components.