Nuclear 3,5,3′-Triiodothyronine Receptors in Skeletal Muscle of Normal and Small-for-Gestational Age Newborn Piglets

Abstract

The number of nuclear T₃ receptors in the longissimus dorsi muscle has been determined in normal and runt (intrauterine growth-retarded) newborn piglets. Values of maximal binding capacity (B_max), as calculated by Scatchard analysis, were 48.2 ± 4.3 and 39.7 ± 4.7 mol × 10^––¹⁴·mg DNA^––1 (mean values ± SEM) for controls and runts respectively (p < 0.01; n = 13 pairs of littermates). The lower B_max in the runts may help to explain their reduced metabolic rate and lower respiratory enzyme activities in skeletal muscle, compared with controls of normal birth weight.

Pregnancy, parturition and neonatal development: interactions between nutrition and thyroid hormones

“…A similar response could be observed in utero as maximal T3 binding capacity is lower in runt (i.e. intra-uterine growth retarded) compared with normal-sized piglets (Dauncey & Geers, 1990).…”

Endocrine Interactions in the Control of Fetal Growth

“…For example, in rats with uterine artery ligation, bodyweight and plasma T 4 concentrations are positively correlated in the pups at 20-21 days of gestation and at birth [25]. In addition, thyroid hormone receptor binding in skeletal muscle is reduced in newborn runt compared to normal-sized piglets [26].…”