Apomorphine-induced growth hormone-release in African catfish (Clarias gariepinus) is related to the animal's nutritional status     

O. Lescroart  I. Roelants  V.M. Darras  E.R. Kühn  F. Ollevier 《Fish physiology and biochemistry》1998,18(4):353-361

In African catfish the dopamine agonist apomorphine (APO) stimulates in vivo growth hormone (GH) release. The present study demonstrates that the potency of APO to stimulate plasma GH levels is affected by the nutritional status of the fish. The effect of starvation on APO induced GH release was investigated in sexually mature and immature catfish. Administration of APO clearly stimulated plasma GH levels in mature catfish that had been starved for 3 and 5 weeks, while no effect could be observed prior to starvation. This increased responsiveness to the GH stimulating action of APO was also demonstrated in fasted immature fish, though it was only evident in fish starved for a prolonged period (19 days or more). The importance of the duration of the starvation period suggests that the enhanced responsiveness is the result of physiological adaptations to starvation rather than an acute effect of food deprivation.  相似文献   

The regulatory effects of thyrotropin-releasing hormone on growth hormone secretion from the pituitary of common carp in vitro   总被引：1，自引：0，他引：1  

Xin-Wei Lin  Hao-Ren Lin  Richard E. Peter 《Fish physiology and biochemistry》1993,11(1-6):71-76

The effects of thyrotropin-releasing hormone (TRH) on growth hormone (GH) and gonadotropin (GtH) release, and the influences of somatostatin (SRIF), the dopamine agonist apomorphine (APO) and extracellular calcium on basal and TRH-induced GH release were examined using an in vitro perifusion system for pituitary fragments of common carp (Cyprinus carpio). Five minute pulses of different dosages of TRH stimulated a rapid and dose-dependent increase in GH release from the perifused pituitary fragments with an ED₅₀ of 9.7 ± 2.3 nM. TRH was ineffective on GtH release. SRIF significantly inhibited basal and TRH-induced GH release from the perifused pituitary fragments, and the effects of SRIF were dose-dependent. APO induced a dose-dependent increase in basal and TRH-stimulated GH release from the perifused pituitary fragments. Increasing the concentrations of extracellular calcium from 0 mM to 1.25 mM resulted in an increase in basal and TRH-induced GH release. The high dose of calcium (6.25 mM) caused a slight decrease in basal and TRH-induced GH release compared with those at a concentration of 1.25 mM.

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Résumé Les effets de la thyrotropine (TRH) sur la sécrétion d'hormone de croissance (GH) et de gonadotropine (GTH), et de la somatostatine (SRIF), de l'apomorphine (APO), antagoniste dopaminergique, et du calcium extracellulaire sur les sécrétions basale et stimulée de GH ont été étudiées in vitro par périfusion, de fragments d'hypophyses de carpe (Cyprinus carpio). Des applications de 5 minutes de TRH à différentes concentrations induisent une stimulation rapide et dose dépendante de la sécrétion de GH (ED₅₀ = 9.7 ± 2.3 nM). Le TRH est sans effet sur la sécrétion de GTH. Le SRIF inhibe la sécrétion basale de GH ainsi que la résponse hypophysaire à l'action du TRH. Son action est dose dépendante. L'apomorphine induit une augmentation dose dépendante de la sécrétion basale de GH et potentialise l'action du TRH sur la stimulation de la sécrétion de GH. Des effets équivalents sont induits par des concentrations croissantes de calcium extra cellulaire de 0 à 1.2 mM, alors qu'à une concentration de 6.25 mM des effets opposés sont obtenus.

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