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

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Binding of 125I-labelled [Tyr1]-somatostatin (125I-[Tyr1]-SRIF) to pituitary caudal lobe membranes was suppressed in immature chickens 1 and 2 h after i.v. administration of unlabelled SRIF at concentrations of 1-100 micrograms/kg. In-vitro preincubation of chicken pituitary glands for 0.5-4.0 h with 0.1 mumol SRIF/l similarly reduced the binding of 125I-[Tyr1]-SRIF to caudal lobe membrane preparations. After a 4-h incubation in 0.1 mmol SRIF/l, the withdrawal of SRIF from the incubation media was accompanied 4 h later by a partial recovery in the binding of 125I-[Tyr1]-SRIF to pituitary membranes. Passive immunoneutralization of endogenous SRIF resulted in a prompt (within 1 h) and sustained (for at least 24 h) suppression of 125I-[Tyr1]-SRIF binding to pituitary membranes. The i.m. administration of cysteamine (300 mg/kg) to 12-week-old birds depleted hypothalamic SRIF stores and decreased the density of 125I-[Tyr1]-SRIF-binding sites in the caudal and cephalic lobes of the chicken pituitary gland. The reduction in SRIF content and in SRIF-binding sites occurred within 1 h of cysteamine administration and was maintained for at least 24 h. In 6-week-old birds, cysteamine (300 mg/kg) administration suppressed pituitary binding of 125I-[Tyr1]-SRIF for at least 5 days. Circulating concentrations of GH were markedly decreased 1 and 4 h after cysteamine injection, but not after 24 h.(ABSTRACT TRUNCATED AT 250 WORDS)

Section: Homologous Regulation Of Srif-binding Sitessupporting

confidence: 66%

Homologous and heterologous regulation of somatostatin-binding sites on chicken adenohypophysial membranes

Harvey

Baidwan²,

Attardo³

1990

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“…In rats, Koshimizu (1983) found no age-related vari¬ ations in the molecular characteristics of SLI in pan¬ creatic and gastrointestinal tissues. Larger molecular forms of somatostatin were also observed in the ven¬ tral and dorsal lobes of the neonatal and adult duck pancreas, one was similar to that found in the hypo¬ thalamus (Foltzer et al 1987), and the other was similar to 'big' somatostatin detected in plasma (Di Scala-Guenot et al 1984). The pancreas may be able to secrete 'big' somatostatin into the plasma of neonatal and adult ducks.…”

Section: Discussionsupporting

confidence: 52%

“…An age-related decline in plasma SLI levels without modifications in the molecular forms has been observed in ducks during post-hatch growth (Foltzer, Harvey & Mialhe, 1987). As the adult duck pancreas is rich in SLI and contains molecular forms identical to those found in plasma (Di Scala-Guenot et al 1984, it may be the main source of circulating SLI.…”

Section: Introductionmentioning

confidence: 97%

Pancreatic somatostatin, glucagon and insulin during post-hatch growth in the duck (Anas platyrhynchos)

Foltzer¹,

Harvey²,

Mialhe³

1987

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Pancreatic somatostatin-like immunoreactivity (SLI), immunoreactive insulin (IRI) and glucagon-like immunoreactivity (GLI) were measured during growth in ducks. The content of each hormone increased progressively but at different rates in the dorsal, ventral and splenic lobes of the pancreas. In the almost fully grown duck, the splenic lobe contained 80 and 63% of the total content of GLI and SLI respectively but low levels of IRI (23%), which were highest in the dorsal lobe (53%). In contrast to the hormonal content, only total GLI concentrations increased during development, the SLI concentrations remaining stable and IRI concentrations declining during growth. Gel filtration of pancreatic extracts indicated that most of the SLI in the pancreas of young and adult birds was somatostatin-14, although somatostatin-28 was present in the ventral lobe of young birds and larger molecular forms were present in the ventral and dorsal lobes. These changes in pancreatic hormonal content and concentration are dissimilar to age-related changes in SLI, GLI and IRI previously observed in the plasma of ducks. Plasma levels of pancreatic hormones may thus be controlled by hormonal and/or neutral factors during post-hatch growth.

“…How¬ ever, higher doses of hpGRF are required to stimulate GH release in adult than in younger birds (Harvey & Scanes, 1984;Proudman, 1984). The GH response to GRF is also blunted in the ageing rat ( (Foltzer, Harvey & Mialhe, 1987) and be partly responsible for the decrease in basal plasma GH previously observed in growing ducks (Foltzer et al 1981). In support of this view, somatostatin inhibited hpGRF-induced GH release in ducklings in a dose-related manner (Fig.…”

Section: Discussionmentioning

confidence: 59%

Plasma growth hormone, somatostatin, insulin and glucagon inter-relationships during infusion of human pancreatic growth hormone-releasing factor in young and adult ducks (Anas platyrhynchos)

Foltzer-Jourdainne¹,

Harvey²,

Karmann³

et al. 1987

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Human pancreatic GH-releasing factor (hpGRF) increased the concentrations of plasma GH when infused i.v. into immature ducks. A dose-dependent increase in plasma GH was observed within 10 min of the start of infusion and was maintained during the 30-min infusion period. Simultaneous infusion of somatostatin S-14 prevented the increase in plasma GH induced by hpGRF, but when the infusion had finished there was a rebound increase in plasma GH. Infusion of the highest dose of hpGRF (800 ng/kg per min) in adult ducks had no significant effect on plasma GH. Plasma somatostatin concentrations were reduced during the infusion of hpGRF in young but not in adult ducks. This observation suggests that the stimulatory effect of hpGRF on GH secretion may be partly due to its inhibitory effect on somatostatin secretion. Infusion of hpGRF in ducklings also increased the concentrations of glucagon and decreased levels of insulin in the plasma. Peripheral plasma glucagon and insulin levels in adult ducks were unaffected by hpGRF infusion. These results indicate that in ducklings, hpGRF increases plasma GH and glucagon concentrations and lowers plasma somatostatin and insulin levels. In the adult, these hormonal responses to hpGRF are not maintained. The highly stimulatory effect of hpGRF on GH secretion in ducklings may explain why plasma GH concentrations are high in these birds.