Plasma concentrations of Luteinising hormone, follicle stimulating hormone, androgen, growth hormone, Prolactin, Thyroxine and Triiodothyronine during growth and sexual development in the cockerel

Temporal plasma GH secretory patterns were measured in cannulated male and female meat-type chickens of two commercial strains at 17, 38 and 60 days of age. Pulse height, amplitude and baseline values were similar in both male and female chickens at 17 days of age, with high amplitude and low baseline values. However, by 38 days of age pulsatile GH secretion was not detectable in females, whereas males exhibited a continued pulsatile secretory pattern similar to that at 17 days of age. Pulsatile GH secretion was not evident in either males or females at 60 days of age. These results clearly demonstrate a sexually dimorphic ontogeny of GH secretion in meat-type chickens.

Section: Resultsmentioning

confidence: 98%

Diminution of pulsatile growth hormone secretion in the domestic fowl (Gallus domesticus): evidence of sexual dimorphism

Johnson

1988

“…However, castration does not affect the age-related decline in GH secretion (Scanes & Johnson, 1984) and plasma concentrations of thyroxine, tri-iodothyronine, insulin, glucagon and corticosterone are not increased during growth (Harvey & Phillips, 1980;Foltzer et al 1981;Sterling, Sharp, Klandorf et al 1984). Hypothalamic and/or peripheral somatostatin may, however, participate in the inhibition of GH during growth.…”

Section: Introductionmentioning

confidence: 98%

Somatostatin-like immunoreactivity in duck plasma, hypothalamus and neural lobe during post-hatch growth: comparison with plasma and pituitary growth hormone concentrations

Foltzer¹,

Harvey²,

Mialhe³

1987

Self Cite

Variations in the concentrations of plasma and pituitary GH were determined in ducks for 66 and 87 days after hatch, and compared with somatostatin-like immunoreactivity (SLI) in the plasma, hypothalamus and neural lobe. Plasma GH levels gradually decreased during growth, while pituitary GH content increased. The concentration of pituitary GH increased during the first 3 weeks of age and remained relatively constant thereafter. The decline in plasma GH concentration was paralleled by a similar fall in the level of plasma SLI. While the content of hypothalamic SLI increased during development, the SLI concentration was maximal at 14 days of age and lowest in adults. The content and concentration of SLI in the neural lobe, in contrast, increased progressively during development. Gel filtration of hypothalamic and neural lobe extracts demonstrated that both young and older birds had two main peaks of SLI, corresponding to somatostatin-14 and somatostatin-28, and a third, larger form. The elution pattern of plasma SLI was similar in young and older birds and was principally composed of a large molecular species ('big' somatostatin), although an additional small peak eluting between somatostatin-28 and somatostatin-14 was eluted from a large pool of plasma from 90-day-old ducks. These results suggest that increased plasma GH levels in young birds do not result from a hypothalamic somatostatin deficiency nor from variations in molecular forms of SLI, and that the age-related decline in plasma GH concentration is not due to a deficiency in pituitary GH content. The decline in the circulating GH level during growth is probably due to an increase in hypothalamic somatostatin release.

“…Factors which contribute to this change in the nature of the association between GH binding and plasma GH concentration, and, potentially, regu¬ lation of hepatic GH binding by GH, are unknown; however, other hormones including insulin and thyroxine are known to influence positively GH bind¬ ing in other tissues (Gause & Eden, 1985), and plasma concentrations of such hormones undergo post-hatch developmental changes in poultry as well (VasilatosYounken, 19866;Goddard, Wilkie & Dunn, 1988;Sterling, Sharp, Klandorf et al 1984). Thus, other hor¬ mones/factors may interact with GH at a given stage of development to alter the apparent relationship of GH to target tissue GH binding.…”

Section: Resultsmentioning

confidence: 98%

Ontogeny of growth hormone (GH) binding in the domestic turkey: evidence of sexual dimorphism and developmental changes in relationship to plasma GH

Vasilatos‐Younken

Gray

Nestor

et al. 1990

The post-hatch ontogeny of hepatic GH binding and its relationship to GH plasma profile characteristics in male and female turkeys of slow- (RBC-2) and fast-growing (F; selected from RBC-2) genetic lines were determined. Specific binding of 125I-labelled recombinant chicken GH to crude hepatic membrane preparations (100,000 g pellet) was determined at 2, 4, 8, 14 and 24 weeks of age for both total (occupied plus free; 4 mol MgCl2/l pretreatment) and free (without MgCl2 pretreatment) binding sites. Characteristics of the plasma GH profile were measured at each age by serial blood sampling through indwelling jugular vein catheters. When specific binding to either free or total sites was expressed on a whole organ basis (i.e. hepatic GH-binding capacity/bird), binding increased dramatically (P less than 0.0001) with increasing age over both lines and sexes. Total binding capacity (free plus occupied sites) per bird was greater for females than for males at 24 weeks of age (P less than 0.04), as birds reached sexual maturity, but did not differ between fast- and slow-growing lines at any age. Available binding capacity (free sites) per bird was greater for the faster growing F than RBC-2 line at the older ages when body size was most divergent (14 and 24 weeks of age; P less than 0.01, P less than 0.06 respectively), but did not differ between sexes. Correlation analysis at individual ages revealed a progressive change in the nature of the relationship between hepatic GH binding, plasma GH and somatic growth.(ABSTRACT TRUNCATED AT 250 WORDS)