Reciprocal changes in serum 3,3′,5′-tri-iodothyronine concentration and the peripheral thyroxine inner ring monodeiodination during food restriction in the young pig

Abstract

Utilizing the difference in pH optima between two distinct enzyme systems responsible for the thyroxine (T4) inner and outer ring monodeiodination, and a specific radioimmunoassay for iodothyronines, the net T4 conversion to 3, 3', 5'-tri-iodothyronine (rT3) and 3, 5', 3'-tri-iodothyronine (T3) in growing pigs kept under various food restrictions was determined in vitro. It has been found that fasting lowers deiodination of T4 to T3 by liver and kidney homogenates. The conversion of T4 to rT3 was reduced in the liver but not in the kidney, unless the animals were completely fasted. During food restriction serum T4 and T3 decreased whereas rT3 increased, which indicated that the serum rT3 level is not a good reflection of T4 to rT3 converting activity in the liver or kidney. The data suggest that a rise in rT3 reflects a lowered degradation rate of the hormone or an increased secretion by the thyroid gland rather than changes in rT3 neogenesis in the periphery.

Neonatal levels of plasma thyroxine in male and female calves fed a colostrum or immunoglobulin diet or fasted for the first 28 hours of life

“…An increase was noted in humans (Azizi, 1978 ;Burman et al, 1979 ;Suda et al, 1978), birds (May, 1978 ;Almeida and Thomas, 1981) and rabbits (Takagi et al 1978), but rats (Chopra, 1980 ;Hastings and Zeman, 1979 ;Heinen et al, 1981), piglets (Slebodzinski et al, 1982) and ruminants (Bahnak et al, 1981 ;Blum et a/., 1980 ;Tveit and Almlid, 1980) show a decrease.…”

“…This may be because not enough samples were studied or that they were not collected at the exact postpartum time when the transient rise occurred. On the contrary, the frequent and precise sampling practiced by Davicco et al (1982) (Balsam and Ingbar, 1979 ;Kaplan and Utiger, 1978 ;Naito et al, 1981) and piglets (Slebodzinski et al, 1982), has been shown to result in a decrease of circulating T3 in these species (Chopra, 1980 ;Hastings and Zeman, 1979 ;Heinen et al, 1981 andSlebodzinski et al, 1982, respectively) ; this phenomenon has also been shown in humans (Azizi, 1978 ;Burman et al, 1979 ;Suda et al, 1978), adult sheep (Blum et al, 1980), growing bulls Tveit and Almlid, 1980), deer (Bahnak et al, 1981), chickens (May, 1978) …”

Peroral administration of triiodothyronine (T3) affects absorption of immunolactoglobulins in calves

“…Boyd and Hogg (1981) failed to find a correlation between serum T 4 and lg concentrations in the calf. However, Levieux (1978, 1980) The thyroid hormones T 4 , T 3 and rT 3 were measured in the serum by radioimmunoassay (Slebodziriski et al, 1982). The metabolic effects of administered T Q and T 3 were traced by means of changes in the total serum proteins (TP), nonesterified fatty acids (NEFA), triglycerides (TG), serum glucose and cholesterol.…”

Ontogenic Characterization of Type I and II Thyroxine 5′-Monodeiodinases in Brown Adipose Tissue from Fetal and Newborn Rabbits

“…The zero-time tubes were prepared by addition of ethanol before that of the enzyme preparation. After storage for 24 h at -2 0 °C the samples were centrifuged for 15 min at 3,000 g and the iodothyronine in ethanol extracts was deter mined using radioimmunoassay procedure [8].…”

“…The cross-reactivity of the antibodies was negligible [8], Each sample was determined in quadruplicate. Mean intra-and inter assay coefficients of variations were 3.4 and 7.6% for T3.…”