Effects of salinity, hypophysectomy, and prolactin on whole-animal transepithelial potential in the tilapia Oreochromis mossambicus

Young, Paciencia S.; McCormick, Stephen D.; Demarest, J. R.; Lin, Richard J.; Nishioka, Richard S.; Bern, Howard A.

doi:10.1016/0016-6480(88)90267-5

Cited by 35 publications

(15 citation statements)

References 30 publications

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“…[Ca 2 +] i and E (Table 3) in tilapia hatched larvae were unavailable in the present study and were assumed to be close to the plasma Ca 2 + concentration, 2.5 mM, (Pratap et al 1989) and the transepithelial potential of whole animal or isolated opercular membrane, 3-13 mV, in tilapia adults (Young et a. 1988;McCormick et al 1992).…”

Section: Discussionmentioning

confidence: 99%

Calcium balance in embryos and larvae of the freshwater-adapted teleost, Oreochromis mossambicus

Hwang

Tsai

Tung

1994

Fish Physiol Biochem

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Changes in Ca(2+) content and flux, and the development of skin chloride cells in embryos and larvae of tilapia, Oreochromis mossambicus, were studied. Tilapia embryos hatched within 96h at an ambient temperature of 26-28°C. Total body Ca(2+) content was maintained at a constant level, about 4-8 nmol per individual, during embryonic development. However, a rapid increase in body Ca(2+) level was observed after hatching, 12.8 to 575.3 nmol per individual from day 1 to day 10 after hatching. A significant influx and efflux of Ca(2+) occurred during development, with the average influx rate for Ca(2+) increasing from 5.9 pmol mg(-1) h(-1) at 48h postfertilization to 47.8 pmol mg(-1) h(-1) at 1 day posthatching. The skin was proposed as the main site for Ca(2+) influx before the development of gills, and the increased Ca(2+) influx may be ascribed to gradual differentiation of skin surface and chloride cells during embryonic development. Ca(2+) efflux was 16-56 pmol mg(-1) h(-1) in 1-day-old larvae. The resulting net influx of Ca(2+), 10-12 pmol mg(-1) h(-1), accounted for the increased Ca(2+) content after hatching. When comparing the measured and estimated ratios of efflux and influx, active transport was suggested to be involved in the uptake of Ca(2+). Chloride cells, which may be responsible for the active uptake of Ca(2+), started to differentiate in the skin of embryos 48h after fertilization, and the density of chloride cells increased following the development. A possibility of active transport for Ca(2+) in early developmental stages of tilapia is suggested.

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Section: Discussionmentioning

confidence: 99%

Calcium balance in embryos and larvae of the freshwater-adapted teleost, Oreochromis mossambicus

Hwang

Tsai

Tung

1994

Fish Physiol Biochem

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“…Both tiPRLs behave similarly in restoring the hydromineral balance of hypophysectomized tilapia transferred to fresh water (Specker et al 1985;Young et al 1988). However, Specker et al (1989) have shown that the salamandrid integumental bioassay can distinguish between the two prolactin variants.…”

Section: Introductionmentioning

confidence: 95%

Evidence that two tilapia (Oreochromis niloticus) prolactins have different osmoregulatory functions during adaptation to a hyperosmotic environment

Aupérin¹,

Rentier-Delrue²,

Martial³

et al. 1994

Journal of Molecular Endocrinology

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Two forms of prolactin (tiPRLI and tiPRLII), with only 69% sequence identity, have been previously described in the cichlid fish tilapia (Oreochromis species). In the present study we have attempted to investigate the biological activity of these two prolactin forms during adaptation to a hyperosmotic environment. For this purpose, we have developed two highly sensitive (sensitivity: 0.05 ng/ml) and specific (cross-reactivity < 0.04%) radioimmunoassays for tiPRLI and tiPRLII, using recombinant hormones. When fish were directly transferred from fresh to brackish water, the measured levels of plasma tiPRLI and tiPRLII dropped abruptly until 12 h after transfer. Thereafter, plasma tiPRLII remained stable (around 0.5 ng/ml) until the end of the experiment, whereas plasma tiPRLI continued to decrease to undetectable levels. These different patterns of change are reflected in the calculated ratio of plasma tiPRLII to tiPRLI, which increased from 2-3 in fresh water-adapted fish to over 10 in fish which had spent 3 days or more in brackish water. The pituitary contents of tiPRLI and tiPRLII varied in a qualitatively similar fashion after transfer to brackish water. The tiPRLI content dropped continuously after 12 h, reaching one-twelfth of its initial level after 2 weeks. The pituitary tiPRLII content, on the other hand, did not decrease significantly until day 7, and after a 2-week exposure to brackish water it had only decreased by 50%. When injected into tilapia adapted to brackish water, both ovine prolactin and recombinant tiPRLI induced a clear dose-dependent ion-retaining effect. In contrast, the effect induced by tiPRLII treatment was markedly smaller and not dose-dependent. Northern blot analysis of tiPRL mRNAs using either a tiPRLI or a tiPRLII cDNA probe indicated the presence of two mRNAs differing in size: a 1.7 kb mRNA coding for tiPRLI and a 1.3 kb mRNA coding for tiPRLII. After transfer to brackish water, levels of the two mRNAs decreased similarly. The present study indicates that, in O. niloticus, the two forms of prolactin have different osmoregulatory roles during adaptation to brackish water. Accordingly, their synthesis are differentially regulated after transfer to a hyperosmotic environment, presumably at a post-transcriptional level.

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“…The two tPRLs have been demonstrated to show no central differentiation in the regulation of their synthesis and release (30), nor a difference in the activities of osmoregulatory physiology in tilapia (29,30,34), although only tPRL188 showed the function of GH, promoting growth in the intact juvenile tilapia (29). The present results do not provide information for the two tPRLs, however it will be an interesting challenge to localize two tPRLs in tilpaia pituitary with immunocytochemical method.…”

Section: Discussionmentioning

confidence: 99%

“…Tilapia (Oreochromis mossambicus), an euryhaline species, has been used frequently for study of the physiology of PRL (6,7,14,18,(32)(33)(34). The PRL cells in tilapia have been identified with antisera to tilapia PRL (tPRL) or salmon PRL (sPRL) at light microscopic level (19,20).…”

mentioning

confidence: 99%

Immunoelectron Microscopical Study of Prolactin in Pituitary of Tilapia (Orochromis mossambicus).

Hwang

Wang

1993

Acta Histochem. Cytochem

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Protein A-gold method was used for cytochemical localization of prolactin (PRL) in the secretory cells in the tilapia (Oreochromis mossambicus) pituitary. Antiserum to chum salmon prolactin (sPRL) was used for this study. Effects of fixation on the antigencity of PRL were examined, and the antigenicities of PRL in pituitaries of seawater (SW)-and freshwater (FW)-adapted tilapia were compared.The antiserum to sPRL reacts selectively only with the secretory granules in the specific cells, i, e., the presumptive PRL cells, in the rostral pars distalis, but never reacts with the other cellular compartment of the PRL cells nor with other cell types in the tilapia pituitary. The findings have been confirmed by the control experiments in which preincubating the antiserum with purified sPRL abolished all the immunoreactivity.PRL cells which have been fixed with 4% paraformaldehyde for 2 to 12 hr, do not show any significant difference in antigenicity preservation, but show a better ultrastructure in longer fixation periods. Addition of 2.5% glutaraldehyde to paraformaldehyde could greatly enhance the ultrastructural preservation but concomitantly might cause a loss of 30% of the antigenicity.Post fixation with 1% osmium tetroxide improves the membranous ultrastructure of organelles, however reduced the PRL antigenicity by 50%.The PRL antigenicity (number of protein A-gold binding per PRL granule) in FWadapted tilapia is 1.5 times that in SW-adapted one. Thus, protein A-gold immunocytochemical method is suggested to be suitable for evaluation of the activity of PRL cells in tilapia reared in different environments.

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Effects of salinity, hypophysectomy, and prolactin on whole-animal transepithelial potential in the tilapia Oreochromis mossambicus

Cited by 35 publications

References 30 publications

Calcium balance in embryos and larvae of the freshwater-adapted teleost, Oreochromis mossambicus

Calcium balance in embryos and larvae of the freshwater-adapted teleost, Oreochromis mossambicus

Evidence that two tilapia (Oreochromis niloticus) prolactins have different osmoregulatory functions during adaptation to a hyperosmotic environment

Immunoelectron Microscopical Study of Prolactin in Pituitary of Tilapia (Orochromis mossambicus).

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