Insulin like growth factor I reduces thyroid hormone receptors in the rat liver. Evidence for a feed-back loop regulating the peripheral thyroid hormone action

PELLIZAS CLAUDIA G, COLEONI ALDO H, COSTAMAGNA MARÍA E, DI FULVIO MAURICIO, MASINI-REPISO ANA M

JOURNAL OF ENDOCRINOLOGY

The Dorset Press, Dorchester

Lugar: Dorset, Great Britain; Año: 1998 vol. 158 p. 87 - 87

0022-0795

b> : Tri-iodothyronine (T3) is known to be involved in the regulation of the growth hormone (GH)-insulin-like growth factor I (IGF-I) axis. In previous studies we demonstrated that IGF-I and GH reduced the metabolic response to T3 measured as the activity of two T3-dependent enzymes, mitochondrial alpha-glycerophosphate dehydrogenase (alpha-GPD) and cytosolic malic enzyme (ME) in cultured rat liver cells. In this study we analysed in vivo the effect of IGF-I administered to rats on the activity of alpha-GPD and ME. IGF-I (240 micrograms/100 g body weight (BW) every 12 h for 48 h) significantly diminished alpha-GPD (P < 0.01) and ME (P < 0.05) activities. Serum basal glucose concentration was not significantly modified 12 h after the administration of recombinant human IGF-I (240 and 480 micrograms/100 g BW every 12 h for 48h). Under similar conditions, no significant change in serum total thyroxine (TT4) concentratio