[Biphasic action of human growth hormones, of hypophyseal origin or bacterial production, on the lipolysis of rat adipocytes in vitro].

Actions of: human growth hormone resultant from hypophysis: HGH h (contaminated by beta LPH 1%) or produced by bacteria HGH b (pure), beta LPH resultant from human hypophysis, one of the somatomedins: multiplication stimulating activity (MSA), produced from a culture of rat hepatocytes, are considered in lipolysis of rat adipocytes "in vitro": basal, stimulated by epinephrine (0.1 and 1 microgram/ml), and when insulin is present (0.1 and 1 mUI/ml), during two periods I: 0-1 h 30, II: 1 h 30 - 4 h (hormonal addition at time 0). MSA appears to be antilipolytic during the two periods, between 0 and 4 h, with 500 ng/ml. A dose of 200 ng/ml is inactive. Beta LPH is lipolytic: 400 and 230 ng/ml, during phase I. At the ratio of the contaminate of HGH h 1000 ng/ml, resultant from hypophysis: 10 ng/ml, the action is less significant. Human growth hormones HGH h and HGH b appear to be: antilipolytic during the first period 0 1 h 30 with 1000 and 300 ng/ml, and, then lipolytic between 1 h 30 and 4 h with 1000, 300 and 100 ng/ml. The effect is pure with HGH b during the two periods, and, principally, during phase I when there is an absence of lipolytic contaminate. Biphasic action: antilipolytic, lipolytic, ascertained with a pure growth hormone: HGH b "in vitro" represents an effect "per se", non mediated by an eventual "in vivo" action of somatomedins.