HEPATIC-MICROSOMAL MEMBRANE LIPIDIC COMPOSITION AND GROWTH-HORMONE EFFECT IN ADULT MALE-RAT - EVIDENCE FOR A FEMINIZATION PROCESS OF TOTAL PHOSPHOLIPID FATTY-ACID PATTERN

Growth hormone (GH) effects on fatty acid composition and on Delta(5)- , Delta(6)-, Delta(9)-desaturase and palmitic acid elongation activiti es were studied in male rat hepatic microsomes. Sham-operated and hypo physectomized animals were injected with two different dosages of GH, mimicking either the male or female GH secretion pattern. Half the hyp ophysectomized animals received thyroxine and cortisol in concentratio ns chosen to compensate for the lack of thyroid hormones and glucocort icoids. GH, administered to sham-operated or to cortisol/thyroxine-tre ated hypophysectomized rats resulted in an increase in stearic and ara chidonic acid proportions, while palmitic acid percentage was decrease d. Total monounsaturated fatty acids were dramatically reduced by this treatment. Delta(5)-Desaturase and palmitic acid elongation activitie s were increased by GH treatment, while Delta(9)-desaturase activity w as decreased. These GH effects on desaturation and elongation activiti es could explain the modifications in microsomal fatty acid compositio n. Hypophysectomy markedly altered the fatty acid composition by reduc ing arachidonic and stearic acid proportions and increasing the linole ic acid proportion, while Delta(9)-,Delta(5)-desaturase and palmitic a cid elongation activities were decreased. Restoration of most of the f atty acid proportions to control values was realized in hypophysectomi zed animals with a cortisol/thyroxine replacement administered alone o r together with the low dosage of GH mimicking the male secretion patt ern. High GH dosage produces essentially a 'feminization' process of t he fatty acid composition of the hepatic microsomal membrane in male r ats when compared to that of females. (C) 1997 Elsevier Science B.V.