Ontogeny of the Response to Thyroxine (T₄) in the Porcine Fetus: Interrelationships Between Serum T₄, Serum Insulin‐Like Growth Factor‐1 (IGF‐1) and Differentiation of Skin and Several Adipose Tissues

Abstract

HAUSMAN, GARY J AND J THOMAS WRIGHT.Ontogeny of the response to thyroxine (T4) in the Porcine fetus: interrelationships between serum T4' serum insulin-like growth factor-I (lGF-l) and differentiation of skin and several adipose tissues. Obes Res.l996; The temporal aspect of thyroxine (T4) enhanced development of several fetal adipose tissue depots (locations) and skin was examined in the present study. On day 70 of gestation pig fetuses were either hypophysectomized (hypox), hypoxed and implanted with T4 pellets or left intact (control). Subsequently, fetuses were removed for study at either 73, 75, 80, 85 and 90 days of gestation. Serum levels of T4 and insulin-like growth factor I (lGF-1) were significantly elevated by T4 after 3 days of treatment and throughout the study. T4 treatment enhanced development of skin, inner and outer subcutaneous (SQ) adipose tissue and adipocyte lobules around hair follicles (HFL's) but degree of response and response time were tissue or depot dependent. The T4 response time was shortest for skin and HFL's, longest for inner SQ and intermediate for the outer SQ. Considering the entire treatment period, magnitude of the T4 response was much greater for skin and HFL's than for outer and inner SQ tissues.

Endocrine Regulation of Fetal Adipose Tissue Metabolism in the Pig: Ontogeny of Thyroxine Influence

“…Serum hormone and body weight data for the fetal pigs used in this study are reported elsewhere [11]. Briefly, the serum luteinizing hormone concentrations were, as expected, reduced to nondetectable levels by hypophysectomy but unaffected by T4 treatment.…”

Growth and development of adipose tissue and gut and related endocrine status during early growth in the pig: impact of low birth weight

“…In the rat, TH have been reported to be involved in the regulation of adipose tissue development (Blennemann et al, 1992) and intestine maturation during weaning (Hodin et al, 1994). In the pig, available data are consistent with a positive influence of T 4 on adipose tissue development in foetuses (Hausman and Hausman, 1993;Chen et al, 1996;Hausman and Wright, 1996).…”

Endocrine Regulation of Fetal Adipose Tissue Metabolism in the Pig: Interaction of Porcine Growth Hormone and Thyroxine

“…Other notable alterations in the serum profile of preobese fetuses and in fetuses from diabetic dams include increases in thyroid hormones and glucocorticoids (21,22). Our recent studies indicate that treatment of hypophysectomized pig fetuses with either hormone results in specific stimulatory effects on adipose tissue development both in vivo and in vitro (3,4,6,16,18,(33)(34)(35). In addition, combined treatment with both hormones had an additive effect on lipogenesis, lipid accretion, and fat cell cluster development (36,37).…”