Estimation of Half-Life and Metabolic Clearance Rate of Thyrotropin-Releasing Hormone in Sheep Using a Double Antibody Radioimmunoassay

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Abstract
A tripeptide, thyroptropin-releasing hormone (TRH), isolated from hypothalamic tissue has the ability to stimulate release of thyrotropin (TSH) from the pituitary both in vivo and in vitro (Schalley et al., 1966; 1968; Burgus et al., 1969). In addition, exogenous TRH also stimulates release of prolactin (PRL) in most species studied (Davis and Borger, 1972; Convey et al., 1973; Bowers et al., 1973) and, in some cases, growth hormone (GH) Convey et al., 1973; Davis et al., 1976). However, it is not known if TRH is a physiological regulator of either PRL or GH secretion. Elucidation of the physiological actions of TRH is partially dependent upon definition of its endogenous secretory pattern, which requires a sensitive and specific assay system for TRH in biological fluids. Plasma hormone concentration is a function of both secretion rate of the hormone and its rate of clearance from the circulation. The estimation of these physiological parameters is dependent upon knowledge of the kinetic parameters of plasma metabolic clearance rate (MCR), and circulating half-life (t½) of the hormone. Copyright © 1979. American Society of Animal Science . Copyright 1979 by American Society of Animal Science.