Effect of high-protein feed supplements on concentrations of growth hormone (GH), insulin-like growth factor-I (IGF-I) and IGF-binding protein-3 in plasma and on the amounts of GH and messenger RNA for GH in the pituitary glands of adult rams

Clarke, I. J.; Fletcher, Timothy David; Pomares, C. C.; Holmes, J. H. G.; Dunshea, Frank R.; Thomas, Graham H.; Tilbrook, AJ; Walton, P. E.; Galloway, D. B.

doi:10.1677/joe.0.1380421

Cited by 20 publications

(19 citation statements)

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“…46 and G(5)=1.13. These parameters followed the values reported previously [26,27]. The significance of differences between values were analyzed by ANOVA, and that of differences between specific groups was determined by the subsequent use of the Newman-Keuls test.…”

Section: Discussionmentioning

confidence: 97%

Plasma Profiles of Growth Hormone, Prolactin and Insulin-like Growth Factor-I during Gestation, Lactation and the Neonatal Period in Goats.

et al. 1999

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Abstract. The objectives of this research were to characterize plasma profiles of growth hormone (GH), prolactin (PRL) and insulin-like growth factor-I (IGF-I) during gestation and the lactation period in goats, as well as in their suckling growing kids. There were no obvious changes in the GH or PRL profiles during gestation, but secretion of both GH and PRL increased acutely after parturition. The elevated GH concentrations were maintained until 3 months after parturition, whereas the PRL concentrations decreased gradually after parturition. The elevated hormone concentrations are thought to be caused mainly by an increase in the secretory pulse amplitudes. In contrast to the GH and PRL profiles, the plasma IGF-I concentrations during late gestation were significantly higher than the post-parturition concentrations, and the IGF-I concentrations in late gestation decreased gradually until the day of parturition. The plasma GH, PRL and IGF-I concentrations in kids 1 week after birth were high, and concentrations of each hormone decreased thereafter. These results show that the increased secretory potencies of pituitary GH and PRL after parturition are caused mainly by an increase in the secretory pulse amplitudes and that plasma GH is inversely related to plasma IGF-I compared over gestation and the lactation period in goats. Key words: GH, PRL, IGF-I, Gestation, Lactation.(J. Reprod. Dev. 45: [273][274][275][276][277][278][279][280][281] 1999) G estation is a composite of integrated processes, resulting in the successful development of fetuses and the birth of offspring. The energy and nutrient requirements in pregnant animals are increased during gestation [1]. The survival of newborn animals is dependent on an adequate supply of milk secreted from the mammary glands of the mother after parturition [2]. Since growth hormone (GH) regulates many aspects of metabolic activity [3], it is meaningful to examine the GH profiles throughout gestation and during the lactation period in animals. Plasma or serum concentrations of GH and prolactin (PRL) in ruminants have been observed to elevate acutely during the periparturient period [4][5][6][7][8][9]. In these published observations, however, blood samples were usually collected for only a few weeks around parturition, and plasma profiles of GH and PRL have never been examined throughout gestation. Moreover, the blood samples were collected only about once a day, although GH and PRL are known to be secreted in transient pulses [3,[10][11][12][13][14]. PRL is required for the initiation of lactation [15,16]; therefore, it is of interest to determine how the pulsatile secretory patterns of both GH and PRL change throughout gestation and during the lactation period in animals. The anabolic action of GH is

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Section: Discussionmentioning

confidence: 97%

Plasma Profiles of Growth Hormone, Prolactin and Insulin-like Growth Factor-I during Gestation, Lactation and the Neonatal Period in Goats.

et al. 1999

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“…Another study showed that genetically lean ram lambs had a significant higher rate of growth hormone release after receiving synthetic human pancreatic GH-releasing factor analogue than the fat animals [8]. Collectively, these previous studies suggest that GH release is impaired in genetically fat lambs, which might be expected since plasma GH levels are generally correlated with adiposity/body weight in sheep [37,38,39,40]. In the cohort of animals in this study, we did find negative correlations between body weight and GH concentration, fat index and GH pulses, plasma leptin and GH amplitude and GH baseline and ORX and MCH gene expression.…”

Section: Discussionmentioning

confidence: 99%

“…A cannula (Dwellcath, Tuta Labs, Melbourne, Vic., Australia) was inserted into one external jugular vein and connected to a manometer line, and the cannula was kept patent with heparinized (75 U/ml) saline. Serial blood samples (5 ml) were taken every 10 min for 8 h (08.00–16.00 h) into heparinized tubes to measure plasma GH levels, because plasma levels of this hormone are correlated with adiposity/body weight in sheep [37,38,39,40]. …”

Section: Methodsmentioning

confidence: 99%

Expression of Genes for Appetite-Regulating Peptides in the Hypothalamus of Genetically Selected Lean and Fat Sheep

et al. 2009

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Background/Aims: The aim was to determine whether genetic selection of sheep for body composition could be accounted for by changes in the level of expression of genes for appetite-regulating peptides in the hypothalamus. We examined gene expression in the hypothalamus of genetically lean, normal and fat ewes (n = 5/group). Methods: Plasma growth hormone (GH) and metabolic indicators were measured and gene expression in brains was quantified by in situ hybridization. Results: Body weight and voluntary food intake (VFI) were similar between groups, but lean and fat animals respectively had low and high indices of adiposity. GH levels were higher in lean and fat animals than in controls. In the arcuate nucleus (ARC), neuropeptide Y (NPY) expression/cell was higher in the lean animals than in normal animals, but overall NPY expression was similar in fat and normal animals. Pro-opiomelanocortin (POMC) and leptin receptor (ObRb) expression in the ARC was similar across groups. Orexin (ORX) and melanin-concentrating hormone (MCH) expression was inversely correlated to adiposity, being higher in lean and lower in fat animals. Conclusion: Expression of genes for orexigenic neuropeptides is altered in a consistent way. Energy expenditure is reduced by MCH but increased by ORX, so increased expression of the latter may cause increased energy expenditure in the lean animals and vice versa in the fat animals.

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“…Plasma GH concentrations increase during chronic feed restriction in the sheep (Waghorn et al 1987, Clarke et al 1993, in contrast to the rat, which exhibits partial or total suppression of pulsatile GH se¬ cretion under conditions of undernutrition (Tannenbaum et al 1977, Sisk & Bronson 1986). In humans, circulating GH is increased by acute feed restriction, but chronic, severe undernutrition is associated with suppressed GH secretion (Hartman et al 1993).…”

Section: Discussionmentioning

confidence: 99%

“…Extraction and analysis ofpituitary GH and GH mRNA GH was extracted from half of the anterior pituitary gland in 0 m HC1 as described previously (Clarke et al 1993). …”

Section: Methodsmentioning

confidence: 99%

GH, GH-releasing factor and somatostatin in the growing lamb: sex differences and mechanisms for sex differences

Gatford

Fletcher

Rao

et al. 1997

Journal of Endocrinology

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Factors contributing to sex differences in the somatotrophic axis were investigated in growing lambs. In the first experiment, circulating patterns of GH in venous blood, pituitary content of GH and GH mRNA, and median eminence (ME) contents of GH-releasing factor (GRF) and somatostatin (SRIF) were characterized in prepubertal ram and ewe lambs which were pair-fed to remove sex differences in feed intake. Mean and baseline plasma GH concentrations, GH pulse amplitude, and integrated plasma GH were greater in ram lambs than in ewe lambs, but GH interpulse interval did not differ between sexes. The pituitary GH content and ME contents of GRF and SRIF were greater in rams than in ewes, but steady-state levels of mRNA for GH in the pituitary gland did not differ between sexes. A second experiment investigated sex effects on the levels of SRIF in hypophysial portal blood, and found that these did not differ between sexes. We concluded that the presence of sexually dimorphic patterns of GH secretion in the growing lamb is independent of feed-intake differences between sexes. The lack of sex differences in circulating patterns of SRIF in portal plasma implies that there may be a difference in GRF secretion which may produce sexually dimorphic patterns of GH secretion in lamb.

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Effect of high-protein feed supplements on concentrations of growth hormone (GH), insulin-like growth factor-I (IGF-I) and IGF-binding protein-3 in plasma and on the amounts of GH and messenger RNA for GH in the pituitary glands of adult rams

Cited by 20 publications

References 39 publications

Plasma Profiles of Growth Hormone, Prolactin and Insulin-like Growth Factor-I during Gestation, Lactation and the Neonatal Period in Goats.

Plasma Profiles of Growth Hormone, Prolactin and Insulin-like Growth Factor-I during Gestation, Lactation and the Neonatal Period in Goats.

Expression of Genes for Appetite-Regulating Peptides in the Hypothalamus of Genetically Selected Lean and Fat Sheep

GH, GH-releasing factor and somatostatin in the growing lamb: sex differences and mechanisms for sex differences

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