Endocrine studies in young chickens of the Obese strain

Scanes, Colin G.; Gales, Luı́s; Harvey, Steven; Chadwick, A.; Newcomer, W. S.

doi:10.1016/0016-6480(76)90110-6

Cited by 34 publications

(15 citation statements)

References 19 publications

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“…Hyperthyroidism induced by dietary T 4 in turkeys is indeed associated with an elevation in basal body temperature (Bilezikian, Loeb and Bammon, 1980). The depressed growth in the hypothyroid birds is in agreement with previous findings (Scanes et al, 1976 ;Chiasson et al, 1979). The observation that MMI treatment reduced the plasma Sm-C values in these birds suggests that growth reduction in the MMI-treated groups was due to Sm-C deficiency and not only to hypothyroidism.…”

Section: Introductionsupporting

confidence: 91%

Effects of hyper- or hypothyroid status on growth, adiposity and levels of growth hormone, somatomedin C and thyroid metabolism in broiler chickens

Decuypere¹,

Buyse²,

Scanes³

et al. 1987

Reprod. Nutr. Dévelop.

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Section: Introductionsupporting

confidence: 91%

Effects of hyper- or hypothyroid status on growth, adiposity and levels of growth hormone, somatomedin C and thyroid metabolism in broiler chickens

Decuypere¹,

Buyse²,

Scanes³

et al. 1987

Reprod. Nutr. Dévelop.

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“…Synthetic TRH has multiple effects on pituitary function in birds, not only stimulating thyrotrophin (TSH) release (Scanes, 1974;Almeida & Thomas, 1981) but also the secretion of luteiniz¬ ing hormone (LH) (Wentworth, Burke & Birrenkott, 1976;Bonney & Cunningham, 1977;Harvey, Sterling & Klandorf, 1983), prolactin (Harvey, Scanes, Chadwick & Bolton, 1978a;Hall, Harvey & Scanes, 1986) and growth hormone (GH) (Harvey et al 1978a;Harvey, 1983a). TRH is an extremely po¬ tent GH-releasing factor in birds, and the finding of increased GH secretion in hypothyroid birds (Scanes, Lance, Harvey et al 1976;Chiasson, Sharp, Klandorf et al 1979;Harvey et al 1983; Har¬ vey, Scanes & Klandorf, 1988) in which endogenous TRH secretion would be high (Almeida & Thomas 1981), and suppressed GH secretion in hyperthyroid birds (Harvey, 19836;Scanes, Denver & Bowen, 1986) in which endogenous TRH would also be sup¬ pressed (Almeida & Thomas 1981), suggests a phys¬ iological role for TRH in avian GH regulation. This possibility is supported by the prompt and sustained decline in the circulating GH level in chickens fol¬ lowing passive immunoneutralization of their endo¬ genous TRH (Klandorf, Harvey & Fraser, 1985).…”

Section: Introductionmentioning

confidence: 94%

Thyrotrophin-releasing hormone (TRH)-induced growth hormone secretion in fowl: binding of TRH to pituitary membranes

Harvey

Baidwan²

1989

Journal of Molecular Endocrinology

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Heat-labile specific binding sites for [3H]3-methylhistidine2-TRH [( 3H]Me-TRH) were demonstrated on chicken adenohypophysial membranes. These binding sites were of both high affinity (dissociation constant, Kd = 15.53 nM) and low capacity (maximum binding capacity, Bmax = 8.73 pmol/g tissue) and of low affinity (Kd = 104.5 nM) and high capacity (Bmax = 32.41 pmol/g). Binding of [3H]Me-TRH to the pituitary membranes was greater at 4 degrees C than at 39 degrees C and occurred with rate constants (k1) of 1.6 x 10(6) and 3.39 x 10(6) M-1 min-1 respectively. Dissociation of [3H]Me-TRH binding at 4 degrees C occurred with a rate constant (k-1) of 0.125 min-1. Binding sites for [3H]Me-TRH were found in the cephalic lobe of the pituitary gland (the location of most lactotrophs and thyrotrophs) and in the caudal lobe (the location of most somatotrophs). The number of binding sites was greater in the caudal lobe than in the cephalic lobe, although the affinity of [3H]Me-TRH binding did not differ. The binding of [3H]Me-TRH to caudal lobe membranes was displaced by Me-TRH, TRH, pGlu-His-Pro-Gly-NH2 and [Glu1]-TRH, with half-maximal effective doses of 33 nM, 70.7 nM, 1.23 microM and 22 microM respectively, but not by [Phe2]-TRH, TRH free acid or His-Pro-diketopiperazine. The number of caudal lobe binding sites for [3H]Me-TRH in old birds was less than that in young ones, and the number of binding sites was increased in birds deprived of food for 48 h. TRH-induced GH secretion in birds would thus appear to be mediated by specific receptors on caudal lobe somatotrophs, and these results suggest that physiological changes in GH secretion (during growth and periods of fasting) are causally related to the abundance of TRH-binding sites.

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“…Indeed a reduction in GH secretion occurs in hypothyroid animals (Davis & Borger, 1973;Peake, Birge & Daughaday, 1973;Takeuchi, Suzuki & Tsuchiya, 1978), an effect reversed by the administration of thyroxine (T4) (Hervas, Morreale de Escobar & Escobar del Rey, 1976;Coirò et al 1979). However, rather than being stimulatory, the thyroid hormones appear to inhibit GH secretion in avian species, the basal plasma GH level being increased in birds made hypothyroid by thyroidectomy (Harvey, 1982), goitrogen treatment (Chiasson, Sharp, Klandorf, Scanes & Harvey, 1979) or autoimmune thyroiditis (Scanes, Gales, Harvey, Chadwick & Newcomer, 1976). In the present study the effects of T4 and tri¬ iodothyronine (T3) on basal and stimulated plasma GH levels have therefore been investigated in domestic fowl (Gallus domesticus).…”

Section: Introductionmentioning

confidence: 98%

Thyroid hormones inhibit growth hormone secretion in domestic fowl (Gallus domesticus)

Harvey¹

1983

Journal of Endocrinology

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The influence of thyroxine (T4) and tri-iodothyronine (T3) on the secretion of GH in immature fowl was investigated. In birds pretreated with i.m. injections of T4 (100 micrograms/day for 10 days or 250 micrograms/kg for 7 days) or T3 (250 micrograms/kg for 7 days) the basal plasma GH level was markedly reduced. A similar reduction in the basal plasma GH level was also observed 60 min after a single injection or T3 (25 and 250 micrograms/kg) or T4 (250 micrograms/kg). In control birds the concentration of plasma GH was greatly increased (greater than 450 micrograms/l) within 10 min of an i.v. injection of thyrotrophin releasing hormone (TRH; 10 micrograms/kg). In birds pretreated with T3 or T4 the increase in GH concentration after TRH treatment was significantly less than that in the controls. In birds pretreated for 60 min with T3 or T4 the GH response to TRH was inversely dose-related and lowest in T3-treated birds. These results demonstrate that T3 and T4 inhibit GH secretion in birds, which is an effect not observed in mammalian species.

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Endocrine studies in young chickens of the Obese strain

Cited by 34 publications

References 19 publications

Effects of hyper- or hypothyroid status on growth, adiposity and levels of growth hormone, somatomedin C and thyroid metabolism in broiler chickens

Effects of hyper- or hypothyroid status on growth, adiposity and levels of growth hormone, somatomedin C and thyroid metabolism in broiler chickens

Thyrotrophin-releasing hormone (TRH)-induced growth hormone secretion in fowl: binding of TRH to pituitary membranes

Thyroid hormones inhibit growth hormone secretion in domestic fowl (Gallus domesticus)

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