In vitro release of growth hormone from the pituitary gland of tilapia, Oreochromis mossambicus

Nishioka, Richard S.; Grau, E. Gordon; Bern, Howard A.

doi:10.1016/0016-6480(85)90297-7

Cited by 51 publications

(17 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Auperin et al (1997) reported that confinement stress for 1 h reduced plasma GH levels, accompanied by an increase in plasma cortisol levels in the Nile tilapia (O. niloticus). According to Nishioka et al (1985), however, cortisol increased GH release from the organ-cultured pituitary of the Mozambique tilapia. The reason for these inconsistent results remains unclear.…”

Section: Discussionmentioning

confidence: 99%

Dual mode of cortisol action on GH/IGF-I/IGF binding proteins in the tilapia, Oreochromis mossambicus

Kajimura¹,

Hirano²,

Visitacion³

et al. 2003

Journal of Endocrinology

100

View full text Add to dashboard Cite

show abstract

Section: Discussionmentioning

confidence: 99%

Dual mode of cortisol action on GH/IGF-I/IGF binding proteins in the tilapia, Oreochromis mossambicus

Kajimura¹,

Hirano²,

Visitacion³

et al. 2003

Journal of Endocrinology

100

View full text Add to dashboard Cite

show abstract

“…If transient increases in cortisol occur in tilapia, as they do in the eel during SW adaptation (42,43), it would not be surprising that cortisol may serve the dual role of rapidly reducing the secretion of a FW osmoregulatory hormone, prolactin (in concert with elevated osmotic pressure), while simultaneously modifying the activity of osmoregulatory tissues.…”

Section: Discussionmentioning

confidence: 99%

Cortisol rapidly reduces prolactin release and cAMP and 45Ca2+ accumulation in the cichlid fish pituitary in vitro.

Borski

Helms

Richman

et al. 1991

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

During in vitro incubation, prolactin release is inhibited in a dose-related manner by cortisol. This action is mimicked by the synthetic glucocorticoid agonist dexamethasone but not by other steroids tested. Perifusion studies indicate that the inhibition of [3Hjprolactin release by cortisol occurs within 20 min. Cortisol (50 nM) also inhibits cAMP accumulation and reduces 4CaZ+ accumulation in the tilapia rostral pars distalis within 15 nmin. Cortisol's action on prolactin release is blocked in the presence of either the Ca2+ ionophore A23187 or a combination of dibutyryl cAMP and 3-isobutyl-1-methylxanthine, which increase intracellular Ca2+ and cAMP, respectively. Taken together, these fidin suggest that cortisol may play a physiologically relevant role in the rapid modulation ofprolactin secretion in vivo. Our studies also suggest that the inhibition of prolactin release by cortisol is a specific glucocorticoid action that may be mediated, in part, through cortisol's ability to inhibit intracellular cAMP and Ca2+ metabolism. ulation of less accessible and more complexly structured osmosensitive tissues (10).The requirements of FW and SW osmoregulation clearly differ and are in many ways opposite. The relative importance of prolactin in FW osmoregulation and cortisol in SW osmoregulation suggests that prolactin cell function might be sensitive to modification by cortisol. Indeed, a preliminary in vitro study showed that high levels of cortisol suppressed prolactin release during overnight incubations (11). Moreover, the ability of the tilapia prolactin cell to react quickly to osmotic stimulation led us to question whether it might also respond rapidly to cortisol.Here, we present evidence that cortisol exerts a rapid, dose-related inhibition of the release of the smaller of the two tilapia prolactins. This action is accompanied by similarly rapid reductions in the accumulation of cAMP and extracellular 45Ca2l and is specific to cortisol and its synthetic agonist dexamethasone.The tilapia, Oreochromis mossambicus, is a euryhaline teleost fish that occupies habitats ranging from fresh water to salinities far in excess of full-strength seawater (SW). Prolactin and cortisol act in the regulation of the remarkable ability of this fish to adapt to extreme and sometimes rapidly changing salinities.Prolactin plays a central role in the freshwater (FW) osmoregulation of the tilapia and many euryhaline teleost fishes, acting to reduce both water and ion fluxes (1-3). Cortisol, a major corticosteroid in teleosts, including the tilapia, acts in SW osmoregulation by reducing blood osmotic pressure (4).In the tilapia, prolactin-producing cells are segregated into a nearly homogeneous mass in the rostral pars distalis (RPD) (mosm)] containing glucose, glutamine, and Eagle's minimal essential medium (11). The osmotic pressure of the incubation medium was adjusted to 300 mosm (hyposmotic) or 355 mosm (hyperosmotic) with NaCI. Tissues were incubated on a gyratory platform (80 rpm) for 18-20 hr at 28 ± PC under a hum...

show abstract

“…These data are thus the first demonstration of an inhibitory effect of TH on GH release in vivo and in vitro in a teleost species. Indeed, previous studies in teleosts failed to show any significant alterations of GH in response to T 3 in vivo (rainbow trout: Moav & McKeown 1992) and in vitro (tilapia: Nishioka et al 1985, carp: Luo & McKeown 1991.…”

Section: Discussionmentioning

confidence: 95%

“…These data from cattle, humans, birds and reptiles suggest that the more generalized vertebrate pattern of thyroidal regulation of pituitary GH may be inhibitory (Denver & Harvey 1991). In teleosts, the few data available on the action of THs on GH production are contradictory, reporting no effect (Nishioka et al 1985, Luo & McKeown 1991, Moav & McKeown 1992, inhibitory (Baker & Ingleton 1975) or stimulatory (Moav & McKeown 1992, Farchi-Pisanty et al 1995, Melamed et al 1995.…”

Section: Introductionmentioning

confidence: 99%

Evidence for a negative feedback in the control of eel growth hormone by thyroid hormones

Rousseau¹,

Belle²,

Sbaihi³

et al. 2002

Journal of Endocrinology

View full text Add to dashboard Cite

The regulation of growth hormone (GH) by thyroid hormones (THs) has been shown to present species variation. We investigated the regulation of GH in the eel, a representative of an ancient group of teleosts. In vivo administration of triiodothyronine (T 3 ) or thyroxine (T 4 ) significantly reduced pituitary and serum GH levels, as measured by homologous RIA. In order to investigate the ability of THs to regulate GH production directly at the pituitary level, we used a long-term, serum-free primary culture of eel pituitary cells. Both T 3 and T 4 inhibited GH release in a concentration-dependent manner, producing up to 50% inhibition at 10 nM, with an ED 50 of <0·2 nM, within the range of their physiological circulating levels. Other hormones also acting via the nuclear receptor superfamily, such as sex steroids (testosterone, estradiol and progesterone) and corticosteroid (cortisol), had no effect on GH release in vitro, underlining the specificity of the regulatory effect of THs on GH. Measurement of both GH release and cellular content for calculation of GH production in vitro indicated that THs not only inhibited GH release but also GH synthesis. Dot-blot assay of GH messenger RNA (mRNA) using an homologous eel cDNA probe showed a decrease in GH mRNA levels in cells cultured in the presence of T 3 , as compared with control cells. This demonstrated that the inhibition of T 3 on GH synthesis was mediated by a decrease in GH mRNA steady state levels. In conclusion, we demonstrate inhibitory regulation of eel GH synthesis and release by THs, exerted directly at the pituitary level. These data contrast with the rat, where THs are known to have a stimulatory effect and suggest that the pattern observed here in an early vertebrate and also found in birds, reptiles and some mammals including humans, may represent an ancestral and more generalized vertebrate pattern of TH regulation of pituitary GH.

show abstract

In vitro release of growth hormone from the pituitary gland of tilapia, Oreochromis mossambicus

Cited by 51 publications

References 23 publications

Dual mode of cortisol action on GH/IGF-I/IGF binding proteins in the tilapia, Oreochromis mossambicus

Dual mode of cortisol action on GH/IGF-I/IGF binding proteins in the tilapia, Oreochromis mossambicus

Cortisol rapidly reduces prolactin release and cAMP and 45Ca2+ accumulation in the cichlid fish pituitary in vitro.

Evidence for a negative feedback in the control of eel growth hormone by thyroid hormones

Contact Info

Product

Resources

About