Influence of Thyrotrophin-Releasing Hormone on Thermoregulation in Newborn Lambs

Abstract

This study examined the effect of thyrotrophin-releasing hormone (TRH) administration on thermoregulation in the newborn. Twin lambs were either delivered near-term by caesarean section or born vaginally at term. Colonic temperature, O₂ consumption, CO₂ production, breathing and heart rates, plus plasma thyroid hormone and nonesterified fatty acid (NEFA) concentrations and thermogenic activity (i.e. GDP binding) of brown adipose tissue (BAT) were measured. In caesarean section delivered lambs colonic temperature decreased rapidly after birth, a response that was greater in the group designated for TRH treatment, in which colonic temperature fell to below 36.0°C at 80 min of life, prior to TRH administration. At this age colonic temperature had been restored to a mean of 38.70°C in controls. TRH had no influence on the composition or thermogenic activity of BAT. The incidence of shivering was not influenced by TRH, but treated lambs maintained a higher rate of O₂ consumption and ventilation compared with controls after colonic temperature had been restored to 38.56°C. TRH appeared to promote fat oxidation as O₂ consumption remained unchanged and CO₂ production declined by a greater rate in treated lambs, resulting in a lower respiratory quotient compared to controls. Heart rate and plasma concentrations of NEFA increased following TRH administration although this did not result in values greater than controls. Normothermic lambs born vaginally had BAT with a greater thermogenic activity, higher plasma thyroid hormone and NEFA concentrations compared with caesarean section delivered lambs, but a thermogenic response was not observed to TRH despite a rise in thyroid hormone concentrations. In conclusion, TRH can improve thermoregulation, an effect that could be linked to an increase in fat oxidation.

Binding of copper(II) to thyrotropin-releasing hormone (TRH) and its analogs

“…Regions between dashed lines define the following wavelength ranges: A -NNNO (one imidazole, two deprotonated amides, one water or hydroxide); B -NNNN (two imidazoles, two deprotonated amides); C -NNNN (one imidazole, three deprotonated amides). CAChe simulation of Cu(II)-TRH 4 (binding at imidazole 3-N) and Cu(II)-(MeHis2TRH) 4 (binding at imidazole 1-N). The listed energy values are "current energy" of geometry-and hybridization-beautified structures.…”

“…Produced in the hypothalamus, TRH has been found to exist in significant quantities in other brain regions in rats [2,3], which implies other bioactivities. The effects of regulating body temperature [4] and stimulating hepatic blood flow [5] have been reported recently.…”

Influence of endemic goitre areas on thyroid hormones in horses

“…Thyroid hormones are important physiological indices commonly used in studies concerning metabolic rate (Chen and Riley, 1981), animal thermogenesis (McGuire et al, 1991;Bird et al, 1998), central nervous system development and changes in cognitive function in animals and humans (Schantz and Widholm, 2001;Helmreich et al, 2006;Long and Voice, 2007). Their supplementation increases the metabolic rate and promotes significant weight loss with dietary restriction (Graves and Schott, 2002).…”

Physiological variables of horses after road transport

“…Thyroid hormones are important physiologic indices which are commonly used in metabolic rate and animal -E-mail: esterina.fazio@tin.it thermogenesis studies (McGuire et al, 1991;Bird et al, 1998) and their supplementation may increase metabolic rate and promote significant weight loss with dietary restriction. In addition, hormonally mediated events play an important role in central nervous system development and function, and a number of researchers have speculated that changes in cognitive function are also mediated by thyroid hormones in humans and animals (Schantz and Widholm, 2001;Helmreich et al, 2006).…”