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

Goff, Pascale Le; Salbert, Gilles; Prunet, Patrick; Saligaut, Christian; Björnsson, Björn Thrándur; Haux, Carl; Valotaire, Yves

doi:10.1016/0303-7207(92)90111-i

Cited by 19 publications

(7 citation statements)

References 40 publications

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“…In rainbow trout, several arguments suggest the absence of such a regulation. First, in our study, SRIF had similar effects on prolactin released from cultured cells obtained from immature, mature male and mature female rainbow trout; secondly, invivo oestradiol treatment of rainbow trout did not increase the sensitivity of cultured prolactin cells to SRIF (P. Prunet, unpublished data) and thirdly, localization of oestradiol receptor mRNA in rainbow trout pituitary gland using in-situ hybridization indicates the absence of oestrogen receptor synthesis in prolactin cells (Le Goff et al 1992). In order to test the specificity of the inhibitory effect of SRIF on prolactin release, a long-acting SRIF analogue was incubated in our pituitary cell culture system.…”

Section: Discussionmentioning

confidence: 52%

Effect of somatostatin on prolactin in rainbow trout (Oncorhynchus mykiss) pituitary cells in primary culture

Goff¹,

Weil²,

Valotaire³

et al. 1992

Journal of Molecular Endocrinology

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To study the control of prolactin secretion in fish, an in-vitro technique using a monolayer cell culture system of rainbow trout pituitary glands was developed. Such secretion was characterized by measurement of both prolactin release and prolactin mRNA content using a trout prolactin cDNA as a probe. This cell culture technique, already used to study the regulation of gonadotrophin secretion in rainbow trout, was further validated by measuring total DNA and protein content. Both parameters appeared to be stable after 2 days of culture. Studying the effect of somatostatin (SRIF) on prolactin cells indicated that a maximal inhibitory effect (62%) was observed after 24 h of treatment. Significant inhibition of prolactin release was obtained for SRIF doses ranging from 50 nM to 1 microM. However, in the same experiment, SRIF was much more potent as an inhibitor of growth hormone release. Short-term (< 12 h) incubation with SRIF did not induce a significant change in prolactin release, whereas growth hormone release was reduced at as early as 1 h after SRIF exposure. SRIF did not have a significant effect on total prolactin content or prolactin mRNA levels, suggesting the absence of an effect on prolactin synthesis. No increase in the magnitude of the inhibitory effect of SRIF was observed when using pituitary cells from immature, mature male or mature female trout. When comparing effects on primary cultures containing cells from the whole pituitary with a prolactin cell-enriched population, SRIF appeared to have the same inhibitory effect on prolactin release, supporting a direct action of SRIF on prolactin cells. These results provide further support for SRIF being a prolactin-inhibiting factor in rainbow trout and acting as a modulator of a dominant stimulatory control of prolactin release.

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Section: Discussionmentioning

confidence: 52%

Effect of somatostatin on prolactin in rainbow trout (Oncorhynchus mykiss) pituitary cells in primary culture

Goff¹,

Weil²,

Valotaire³

et al. 1992

Journal of Molecular Endocrinology

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“…Treatment with E 2 resulted in a significant increase in pituitary PRL mRNA in juvenile gilthead seabream, and this agrees with a previously observed, dose-dependent increase in pituitary synthesis of two forms of PRL in E 2 -treated tilapia in vivo and in vitro [24,25]. However, in rainbow trout (Oncorhynchus mykiss), E 2 injection (5 g/g body weight) did not result in a significant increase in either PRL mRNA levels or protein levels in the pituitary after 3 days of treatment in immature fish or after a 3-wk treatment period in mature male fish [26]. This was taken to suggest that PRL cells are not regulated by estrogens in this species [26].…”

Section: Discussionmentioning

confidence: 63%

“…However, in rainbow trout (Oncorhynchus mykiss), E 2 injection (5 g/g body weight) did not result in a significant increase in either PRL mRNA levels or protein levels in the pituitary after 3 days of treatment in immature fish or after a 3-wk treatment period in mature male fish [26]. This was taken to suggest that PRL cells are not regulated by estrogens in this species [26]. The dosage and duration of the experiments may nevertheless explain the conflicting results.…”

Section: Discussionmentioning

confidence: 94%

Quantification of Prolactin (PRL) and PRL Receptor Messenger RNA in Gilthead Seabream (Sparus aurata) after Treatment with Estradiol-17β1

Cavaco

Santos

Ingleton

et al. 2003

Biology of Reproduction

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Prolactin (PRL) in fish is considered to be an osmoregulatory hormone, although some studies suggest that it may influence the production of steroid hormones in the gonads. The objective of the present study was to establish if PRL is involved in reproduction of the gilthead seabream-a protandrous hermaphrodite. Adult and juvenile gilthead seabream received implants of estradiol-17beta (E(2)) for 1 wk during the breeding season, and the mRNA expressions of PRL and PRL receptor (sbPRLR) were determined. Northern blot analysis revealed a single pituitary PRL transcript, the expression of which was significantly reduced by E(2) treatment in adults but significantly increased in juvenile fish. In adult gonads, four sbPRLR transcripts of 1.1, 1.3, 1.9, and 2.8 kilobases were observed. A competitive reverse transcription-polymerase chain reaction was developed and used to determine how E(2) treatment alters expression of the gonadal sbPRLR gene. Seabream PRLR was detectable in all samples analyzed by this assay. Levels of sbPRLR mRNA increased significantly (50-fold) after E(2) treatment in adults, but a 24-fold decrease was measured in juveniles. Immunohistochemistry using specific polyclonal antibodies raised against an oligopeptide from the extracellular domain of sbPRLR detected the receptor in spermatogonia and oocytes. Taken together, the preceding results suggest that in the seabream, PRL may act on both testis and ovary via its receptor and that the stage of maturity influences this process. The full characterization and relative importance of the different transcripts of sbPRLR in eliciting the action of PRL in the gonads remain to be elucidated.

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“…In rainbow trout, estrogen receptor (ER) immunoreactivity was detected in the VT and PPa (Salbert et al, 1991;Anglade et al, 1994), and glucocorticoid receptor (GR) immunoreactivity was found in sGnRH neurons (Teitsma et al, 1999). Hybridization signals of ER mRNAs were observed in the pituitary (Goff et al, 1992). Administration of androgens or estrogen increased signals of sGnRH mRNAs in the VT (Amano et al, 1994) and the amounts of sGnRH peptide in the forebrain and the pituitary (Breton and Sambroni, 1996).…”

Section: Underlying Mechanisms and The Hpg-axismentioning

confidence: 95%

Elevation of gene expression for salmon gonadotropin-releasing hormone in discrete brain loci of prespawning chum salmon during upstream migration

et al. 2005

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Our previous studies suggested that salmon gonadotropin-releasing hormone (sGnRH) neurons regulate both final maturation and migratory behavior in homing salmonids. Activation of sGnRH neurons can occur during upstream migration. We therefore examined expression of genes encoding the precursors of sGnRH, sGnRH-I, and sGnRH-II, in discrete forebrain loci of prespawning chum salmon, Oncorhynchus keta. Fish were captured from 1997 through 1999 along their homing pathway: coastal areas, a midway of the river, 4 km downstream of the natal hatchery, and the hatchery. Amounts of sGnRH mRNAs in fresh frozen sections including the olfactory bulb (OB), terminal nerve (TN), ventral telencephalon (VT), nucleus preopticus parvocellularis anterioris (PPa), and nucleus preopticus magnocellularis (PM) were determined by quantitative real-time polymerase chain reactions. The amounts of sGnRH-II mRNA were higher than those of sGnRH-I mRNA, while they showed similar changes during upstream migration. In the OB and TN, the amounts of sGnRH mRNAs elevated from the coast to the natal hatchery. In the VT and PPa, they elevated along with the progress of final maturation. Such elevation was also observed in the rostroventral, middle, and dorsocaudal parts of the PM. The amounts of gonadotropin IIbeta and somatolactin mRNAs in the pituitary also increased consistently with the elevation of gene expression for sGnRH. These results, in combination with lines of previous evidence, indicate that sGnRH neurons are activated in almost all the forebrain loci during the last phases of spawning migration, resulting in coordination of final gonadal maturation and migratory behavior to the spawning ground.

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

Cited by 19 publications

References 40 publications

Effect of somatostatin on prolactin in rainbow trout (Oncorhynchus mykiss) pituitary cells in primary culture

Effect of somatostatin on prolactin in rainbow trout (Oncorhynchus mykiss) pituitary cells in primary culture

Quantification of Prolactin (PRL) and PRL Receptor Messenger RNA in Gilthead Seabream (Sparus aurata) after Treatment with Estradiol-17β1

Elevation of gene expression for salmon gonadotropin-releasing hormone in discrete brain loci of prespawning chum salmon during upstream migration

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