Endocrine regulation of fetal adipose tissue metabolism in the pig: ontogeny of thyroxine influence.
Our previous studies indicated that thyroxine (T4) markedly enhanced adipose tissue development and metabolism when administered to hypophysectomized fetal pigs from days 70 to 90 of gestation. In this study, hypophysectomized (day 70) fetal pigs were implanted with T4 pellets, and blood and adipose tissue samples were obtained upon removal on days 73, 75, 80, or 85 of gestation to examine the time course of T4 response. T4 treatment in hypophysectomized fetuses resulted in an elevation in serum T4 levels by day 73 of gestation, with no further increase on day 80 or 85. Quantitative analysis of subcutaneous adipose tissue indicated that hypophysectomy per se had no influence on lipid deposition, whereas the extent of T4-stimulated lipid deposition increased with fetal age beginning on day 75. Glucose oxidation and lipogenesis in subcutaneous adipose tissue slices was increased by T4 treatment in hypophysectomized fetuses by day 73 of gestation and further increased with additional time of treatment. Hypophysectomy per se induced a slight increase in lipogenesis only on days 80 and 85 of gestation. Basal lipolysis was unaffected by age, hypophysectomy, or T4 treatment. The responsiveness for a variety of lipolytic stimuli was both accelerated and enhanced by T4 treatment in hypophysectomized fetuses. The results indicate that the T4 influence on adipose tissue development (1) is already apparent following only 3 days of hormone treatment in the hypophysectomized fetuses, (2) clearly precedes hypophysectomy-induced alterations in cellular and metabolic development of adipose tissue, and (3) is not mediated exclusively by serum concentrations of the hormone.
Hausman
D B
DB
Department of Foods and Nutrition, University of Georgia, Athens 30602-3622, USA.
Hausman
G J
GJ
Martin
R J
RJ
D000243:Adenosine Deaminase / Q000494:pharmacology; D000273:Adipose Tissue / Q000187:drug effects* / Q000196:embryology* / Q000378:metabolism; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D005227:Fatty Acids / Q000378:metabolism; D005260:Female; D005865:Gestational Age; D005947:Glucose / Q000378:metabolism; D005954:Glucosephosphate Dehydrogenase / Q000378:metabolism; D007016:Hypophysectomy; D007545:Isoproterenol / Q000494:pharmacology; D008055:Lipids / Q000096:biosynthesis; D008066:Lipolysis; D007986:Luteinizing Hormone / Q000097:blood; D010084:Oxidation-Reduction; D011247:Pregnancy; D013552:Swine / Q000196:embryology*; D013974:Thyroxine / Q000097:blood / Q000494:pharmacology*; D014284:Triiodothyronine / Q000097:blood
D000318:Adrenergic beta-Agonists; D005227:Fatty Acids; D008055:Lipids; D014284:Triiodothyronine; D003994:Bucladesine; D007986:Luteinizing Hormone; D005954:Glucosephosphate Dehydrogenase; D000243:Adenosine Deaminase; D005947:Glucose; D007545:Isoproterenol; D013974:Thyroxine