Control of prolactin secretion in teleosts, with special reference to Gillichthys mirabilis and Tilapia mossambica

Nagahama, Yoshitaka; Nishioka, Richard S.; Bern, Howard A.; Gunther, Robert

doi:10.1016/0016-6480(75)90187-2

Cited by 150 publications

(54 citation statements)

References 52 publications

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“…As medium osmolality decreased, the Prl 188 /Prl 177 release ratio increased. Overall, hyposmotically induced release of both Prls from SW-acclimated tilapia showed a lower sensitivity that may be derived from the lower quantity of Prl stored in the pituitaries of these fish (Nagahama et al 1975). Recent evidence also suggests that this difference may result from the diminished ability of Prl cells from SW-acclimated tilapia to initiate osmotic signal transduction.…”

mentioning

confidence: 91%

“…While the discovery of two distinct Prl molecules in tilapia suggested the evolution of distinct actions, no clear differences in osmoregulatory action have been demonstrated (Specker et al 1985). This issue has been recently revisited by Fiol et al (2009), who reported that Prl 177 and Prl 188 activate distinct downstream signalling pathways in transfected HEK293 cells expressing tilapia PrlRs.Early studies have shown greater RPD and Prl cell size (Dharmamba & Nishioka 1968), greater Prl cell activity (Nagahama et al 1975), and greater hypophyseal Prl content (Nicoll et al 1981) in tilapia maintained in FW compared to tilapia maintained in SW. Later, Yoshikawa-Ebesu et al (1995) reported that hyposmotically induced Prl 177 and Prl 188 synthesis is more robust in RPDs of fish acclimated to FW than in RPDs of fish acclimated to SW. Likewise, mRNA levels for both prl genes were higher in pituitaries of tilapia acclimated to FW than in pituitaries of fish acclimated to 1 ⁄ 4 SW or SW (Shepherd et al 1999).…”

mentioning

confidence: 99%

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Prolactin177, prolactin188 and prolactin receptor 2 in the pituitary of the euryhaline tilapia, Oreochromis mossambicus, are differentially osmosensitive

Seale

Moorman²,

Stagg³

et al. 2012

Journal of Endocrinology

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Two forms of prolactin (Prl), prolactin 177 (Prl 177 ) and prolactin 188 (Prl 188 ), are produced in the rostral pars distalis (RPD) of the pituitary gland of euryhaline Mozambique tilapia, Oreochromis mossambicus. Consistent with their roles in fresh water (FW) osmoregulation, release of both Prls is rapidly stimulated by hyposmotic stimuli, both in vivo and in vitro. We examined the concurrent dynamics of Prl 177 and Prl 188 hormone release and mRNA expression from Prl cells in response to changes in environmental salinity in vivo and to changes in extracellular osmolality in vitro. In addition, mRNA levels of Prl receptors 1 and 2 (prlr1 and prlr2) and osmotic stress transcription factor 1 (ostf1) were measured. Following transfer from seawater (SW) to FW, plasma osmolality decreased, while plasma levels of Prl 177 and Prl 188 and RPD mRNA levels of prl 177 and prl 188 increased. The opposite pattern was observed when fish were transferred from FW to SW. Moreover, hyposmotically induced release of Prl 188 was greater in Prl cells isolated from FW-acclimated fish after 6 h of incubation, while the hyposmotically induced increase in prl 188 mRNA levels was only observed in SW-acclimated fish. In addition, prlr2 and ostf1 mRNA levels in Prl cells from both FW-and SW-acclimated fish increased in direct proportion to increases in extracellular osmolality both in vivo and in vitro. Taken together, these results indicate that the osmosensitivity of the tilapia RPD is modulated by environmental salinity with respect to hormone release and gene expression. Journal of Endocrinology (2012) 213, 89-98Introduction A necessary component of the systems that direct osmoregulatory processes are osmoreceptors that detect deviations from salt and water balance and initiate adaptive responses to restore equilibrium. The prolactin (Prl)-secreting cells of the euryhaline Mozambique tilapia (Oreochromis mossambicus) comprise a nearly homogeneous portion of the rostral pars distalis (RPD) of the pituitary (conservatively O95%) and are directly stimulated by physiologically relevant decreases in extracellular osmolality in vitro , Seale et al. 2006b. Consistent with its role as an essential hormone for fresh water (FW) acclimation (reviewed by Hirano (1986), Manzon (2002) and Sakamoto & McCormick (2006)) plasma Prl levels increase in vivo when tilapia are transferred from seawater (SW) to FW (Yada et al. 1994, Seale et al. 2002. The operation of tilapia Prl cells as true osmoreceptors and the anatomical organization of these cells in tilapia RPD provide an accessible model to integrate osmosensing mechanisms with gene transcription, hormone synthesis and hormone secretion (Seale et al. 2005).Hyposmotically induced Prl release from tilapia lactotrophs is dependent on the entry of extracellular Ca 2C through stretch-activated ion channels upon cell swelling (Seale et al. 2003). There is evidence that the influx of extracellular Ca 2C may have distinct intracellular effects depending on the acclimation salinity of the animal fro...

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mentioning

confidence: 91%

mentioning

confidence: 99%

Prolactin177, prolactin188 and prolactin receptor 2 in the pituitary of the euryhaline tilapia, Oreochromis mossambicus, are differentially osmosensitive

Seale

Moorman²,

Stagg³

et al. 2012

Journal of Endocrinology

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“…Although much less developed, available information on teleost fish suggests that estrogens may also regulate PRL cell activity. E, stimulates PRL synthesis in tilapia (Wigham et al, 1977) and markely activates PRL cells in mudsucker and in eel (Nagahama et al, 1975;Olivereau and Olivereau, 1979;Olivereau et al, 1986). In vitro studies using organ-cultured pituitary from tilapia also indicate that estradiol treatment both stimulates spontaneous PRL release when tested in a hyperosmotic environment and promotes stimulation of PRL release by TRH (Barry and Grau, 1986).…”

Section: Introductionmentioning

confidence: 99%

Absence of direct regulation of prolactin cells by estradiol-17β in rainbow trout (Oncorhynchus mykiss)

Goff

Salbert

Prunet

et al. 1992

Molecular and Cellular Endocrinology

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SummaryThe effects of estradiol-17/3 (E,) implants on plasma prolactin (PRL) concentrations, pituitary PRL content and pituitary PRL mRNA levels were examined in rainbow trout (Oncorhynchus mykiss). Intact immature fish treated with 1 mg estradiol-17/? did not show significant changes in both PRL mRNA levels and pituitary PRL content after 3 days of treatment. In a similar experiment, no changes were observed in plasma PRL levels followed during 7 days. Similarly, lack of estradiol-17/3 effect on plasma PRL levels and on final PRL pituitary content was observed in ovariectomized female rainbow trout treated during 48 days with 25 mg estradiol-17P and in mature male fish over a 3-week treatment period. Localization of estradiol receptor (ER) mRNAs in the pituitary was carried out by Northern blot analysis using a full-length rainbow trout estrogen receptor (rtER) cDNA as a probe. The rostra1 pars distalis of the pituitary which contained mostly PRL cells showed the lower amount of rtER mRNA when compared to other parts of the pituitary. Moreover, two mRNAs of different size (3.5 and 1.4 kb) were detected in different parts of the pituitary. Further hybridization experiments using probes containing part of the rtER cDNA (E domain or C and D domains) indicated that the small-sized mRNA (1.4 kb) probably encodes a truncated ER protein lacking hormone binding domain or an ER-related protein. Thus, only the 3.56 kb mRNA appeared to be involved in the regulation of pituitary function by estradiol. In situ hybridization analysis allowed a more precise localization of this rtER mRNA in the pituitary. No labeling was discernible over PRL cells whereas other parts of the pituitary were labeled. Grain counting corroborated this localization. These results indicate that (1) in vivo estradiol-17P treatment did not modify PRL cell activity in rainbow trout, (2) PRL secretion, in this fish species, is not directly regulated by estradiol.

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“…Experiments on pituitary glands in vitro and on pituitary transplants have led to the hypothesis that the effect of environmental salinity on prolactin secre tion is mediated by changes in plasma os molarity or sodium concentration (Naga hama et a I., 1974Wigham and Ball, 1977). Incubation of teleost pituitary glands in hyposmotic fluids activates the prolactin celts, as was concluded from the observation of proliferation of cellular or ganelles, increase in exocytosis, reduction of prolactin content of the pituitary glands, and a rise in bioassayable prolactin in the incubation fluid (Zambrano et al, 1974: Nagahama et al, 1975. A reduction of pro lactin cell activity has been reported after an increase in the sodium content of the culture medium, although not for the pro lactin cells of all species examined (Nagahama et a I., 1974;Baker and Ingleton.…”

Section: Control O F Prolactin Secretionmentioning

confidence: 93%

“…An inhibitory influence by the hypothalamus is undoubtedly one of the mechanisms, but a direct effect of plasma factors is also indicated (Zambrano et a I., 1974;Nagahama et al, 1974Nagahama et al, . 1975Wigham and Ball, 1977).…”

Section: Control O F Prolactin Secretionmentioning

confidence: 99%

The effects of changes in external sodium, calcium, and magnesium concentrations on prolactin cells, skin, and plasma electrolytes of Gasterosteus aculeatus

Bonga

1978

General and Comparative Endocrinology

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Exposure of freshwater fish to freshwater containing calcium and magnesium ions in concentrations found in seawater reduces prolactin cell activity to the low values character istic for seawater fish. When applied in the same concentrations, calcium is more effective than magnesium. High sodium concentrations have only small effects. Transfer of fish to freshwater or seawater with reduced ionic calcium and magnesium levels activates the prolactin cells. In these experiments plasma ionic calcium and sodium levels were negatively correlated with prolactin cell activity, while thickness of the epidermis and density of the epidermal mucocytes were positively correlated with prolactin cell activity. It is concluded that ionic calcium concentration, and not osmolarity or sodium content, is the main en vironmental factor in the control of prolactin secretion in sticklebacks.

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Control of prolactin secretion in teleosts, with special reference to Gillichthys mirabilis and Tilapia mossambica

Cited by 150 publications

References 52 publications

Prolactin177, prolactin188 and prolactin receptor 2 in the pituitary of the euryhaline tilapia, Oreochromis mossambicus, are differentially osmosensitive

Prolactin177, prolactin188 and prolactin receptor 2 in the pituitary of the euryhaline tilapia, Oreochromis mossambicus, are differentially osmosensitive

Absence of direct regulation of prolactin cells by estradiol-17β in rainbow trout (Oncorhynchus mykiss)

The effects of changes in external sodium, calcium, and magnesium concentrations on prolactin cells, skin, and plasma electrolytes of Gasterosteus aculeatus

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