Responses to salinity and the effect of prolactin on whole animal transepithelial potential in the Gobiid teleost, Gillichthys mirabilis

doi:10.1016/0016-6480(85)90078-4

General and Comparative Endocrinology

Volume 60, Issue 3, December 1985, Pages 434-440

This paper is dedicated to the memory of Della Fisher Reid, pioneer investigator of transport physiology in tilapia and dear friend.

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Abstract

Whole-animal transepithelial potential (TEP) of the goby, Gillichthys mirabilis, was measured. TEP was the same whether the electrode was implanted in the dorsal muscle or in the peritoneal cavity. TEP response to different salinities was linear from 0 to 100% seawater, and stable from 100 to 200% seawater. TEP decreased significantly in 225 and 250% seawater, and the fish became dehydrated. Plasma Na and Cl concentrations showed a linear relationship with increase in salinity from 0 to 200% seawater. In hypophysectomized Gillichthys, TEP was significantly lower than in sham-operated fish, but hypophysectomized fish with a rostral pars distalis autotransplant showed TEP similar to that of intact fish. Plasma Na and Cl in hypophysectomized fish were lower than in intact and RPD-autotransplanted fish, suggesting that prolactin is involved in maintaining normal whole-animal TEP.

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Cited by (6)

Pituitary gene expression of somatolactin, prolactin, and growth hormone during Atlantic salmon parr-smolt transformation
2003, Aquaculture
Somatolactin (SL), prolactin (PRL) and growth hormone (GH) belong to the same family of adenohypophyseal hormones. In fish, these hormones have all been linked to several important physiological functions. During salmon smoltification, GH has an important role in stimulating growth and improving hypoosmoregulatory ability. The role of PRL in fish osmoregulation has mostly been linked to survival in fresh water (FW), whereas the physiological functions of SL is less clear, having been linked to reproduction, stress, Ca-regulation and acid–base balance. To obtain more information on the roles and interactions of these hormones during the parr–smolt transformation, juvenile Atlantic salmon in FW were sampled from early-February until late-June. Approximately every 2 weeks, fish were sacrificed and pituitaries sampled for assessment of SL, PRL, and GH mRNA. In addition, fish were transferred to seawater (SW) in late-May, and sampled after 1 and 4 weeks in SW.
Somatolactin mRNA expression did not change during the parr–smolt transformation of the Atlantic salmon, but increased transiently during the first week in SW, a response which may be correlated to stress and/or Ca-balance. PRL and GH mRNA expression increased transiently during the latter part of the parr–smolt transformation of Atlantic salmon. Following SW entry, the PRL mRNA expression decreased, while GH mRNA expression increased further. This indicates that PRL is of importance during the parr–smolt transformation of the Atlantic salmon, probably by counteracting the hypoosmoregulatory effects of GH and cortisol, allowing the fish to maintain osmotic balance during the smoltification process.
Effects of salinity, hypophysectomy, and prolactin on whole-animal transepithelial potential in the tilapia Oreochromis mossambicus
1988, General and Comparative Endocrinology
We have examined whether two recently isolated forms of tilapia (Oreochromis mossambicus) prolactin exert similar effects on osmoregulatory physiology. The effects of salinity, hypophysectomy, and replacement therapy with tilapia prolactins on whole-animal transepithelial potential (TEP), gill Na⁺, K⁺-ATPase activity, and plasma ions were determined. When intact fish adapted to 25% seawater (SW) were transferred to different salinities, TEP reached a steady state after 10 hr; TEP increased with increasing salinity from fresh water (FW) to 75% SW but was stable from 75 to 125% SW. Plasma osmolality, [Na⁺], and [Cl⁻] of these fish 24 hr after salinity change showed that fish in 100 and 125% SW had greater osmotic perturbation than those transferred to lower salinities. Following a 5-day recovery period in 25% SW, hypophysectomized fish transferred to FW for 10 hr had significantly lower TEP and plasma ion levels than either sham-operated fish or intact fish under the same conditions. Injection of hypophysectomized fish with “small” prolactin (tPRL₁₇₇), “large” prolactin (tPRL₁₈₈), or a combination of both (0.5 μg/g body weight) 22 hr and again 20 min prior to transfer from 25% SW to FW, restored TEP and plasma ion levels to those of sham-operated fish. Neither prolactin affected the TEP or plasma ions of sham-operated (intact) fish. Hypophysectomized fish had lower gill Na⁺, K⁺-ATPase activity than sham-operated fish in FW, but prolactin injections as described above did not affect gill Na⁺, K⁺-ATPase activity in either hypophysectomized or sham-operated fish. Our results indicate that the two forms of prolactin are indistinguishable with regard to several aspects of tilapia osmoregulation.
Characterization of ion and acid-base transport in the fresh water adapted mummichog (Fundulus heteroclitus)
1997, Journal of Experimental Zoology
Osmoregulation in the mudskipper, Boleophthalmus boddaerti II. transepithelial potential and hormonal control
1991, Fish Physiology and Biochemistry
Unequal activities of the two tilapia prolactins in the whole-animal transepithelial potential bioassay using the red eft
1989, Fish Physiology and Biochemistry
Whole animal transepithelial potential (TEP) of coho salmon during the parr-smolt transformation and effects of thyroxine, prolactin and hypophysectomy
1987, Fish Physiology and Biochemistry

¹: Present address: Otsuchi Marine Research Center, ORI, University of Tokyo, Otsuchi, Iwate 028-11, Japan.

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General and Comparative Endocrinology

Abstract

References (26)

Hypothalamic control of the pars distalis in fishes, amphibians, and reptiles

Gen. Comp. Endocrinol

Hypothalamic control of ACTH secretion in goldfish. I. Corticotrophin-releasing factor activity in teleost brain tissue extracts

Gen. Comp. Endocrinol

On the electrical gradient across the gill of the sea water-adapted eel

Comp. Biochem. Physiol

Geographic Variation in the Morphology and Physiology of the Gobiid Fishes of the Genus Gillichthys

Sensitivity and specificity of salamandrid integumental transepithelial potential to prolactin

Gen. Comp. Endocrinol

Transepithelial potential measurements in the isolated, perfused head of a marine teleost

J. Exp. Zool

The roles of sodium transport and anion permeability in generating transepithelial potential differences in larval salamanders

J. Exp. Biol

Sodium, chrolide and water balance of the intertidal teleost, Pholis gunnelleus

J. Exp. Biol

Kinetic studies of ion transport by fish gill epithelium

Amer. J. Physiol

Fish gill ionic transport: Methods and models

Biol. Bull

Chloride secretion and conductance of teleost opercular membrane: Effects of prolactin

Amer. J. Physiol

Chloride cells and the hormonal control of teleost fish osmoregulation

J. Exp. Biol

Osmotic regulation in the brackish water teleost

Blennius pholis. J. Exp. Biol

Cited by (6)

Pituitary gene expression of somatolactin, prolactin, and growth hormone during Atlantic salmon parr-smolt transformation

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

Characterization of ion and acid-base transport in the fresh water adapted mummichog (Fundulus heteroclitus)

Osmoregulation in the mudskipper, Boleophthalmus boddaerti II. transepithelial potential and hormonal control

Unequal activities of the two tilapia prolactins in the whole-animal transepithelial potential bioassay using the red eft

Whole animal transepithelial potential (TEP) of coho salmon during the parr-smolt transformation and effects of thyroxine, prolactin and hypophysectomy