Prolactin cell activity and sodium fluxes in tilapia (Oreochromis mossambicus) after long-term acclimation to acid water

Abstract

Please be advised that this information was generated on 2018-05-12 and may be subject to change.,f NERAL AND COMPARATIVE ENDOCRINOLOGY 75, 3 9^5 (1989) Prolactin Cell Activity and Sodium Fluxes in Tilapia (Oreochromis mossambicus) after Long-Term Acclimation to Acid Water G e r t F l i k ,* J o a n A. v a n d e r V e l d e n , ! H e in C. In tilapia exposed for 3 months to water of pH 4.5, prolactin cell activity, as estimated by ultrastructural morphometry and determination of prolactin synthesis in vitro, was signifi cantly higher than in controls from neutral water. Sodium influx from the water was 50% lower than in the controls, indicating impaired branchial sodium uptake mechanisms. In contrast to predictions based on the results of short-term exposure to acid water-which is known to induce an increase of sodium efflux-the sodium efflux rate was reduced to 70% of the control value. It is concluded that tilapia are able to acclimate to acid water by successful control-probably via prolactin-of diffusional sodium losses across the integu ment, in particular the gill surface. This compensates for the impaired sodium uptake, and enables the fish to reestablish a positive sodium balance in acid water.

Prolactin cell activity and sodium balance in the acid-tolerant mudminnow Umbra pygmaea in acid and neutral water

“…In O . mossambicus kept for 4 months under the same controlled condi tions as the mudminnows in the present ex periment, the growth rate was higher at p H 7.0 than at p H 4.5 (Flik et al, 1989). W e consider the higher growth rate of mudmin nows in acid water as further evidence for the exceptional acid tolerance of these fish.…”

“…H o w ever, at p H 4.0 or higher, the initial drop in plasma sodium is restored in the course of the first week in acid water (Wendelaar Bonga et al, 1984), probably as a result of reduction of the acid-induced increase in branchial permeability to ions. W e have shown that after long-term acclimation the 422 WENDELAAR BONGA ET AL branchial permeability to sodium was even reduced to levels significantly below con trol values (Flik et al, 1989). This decrease was associated with a substantial increase in prolactin cell activity.…”

“…WENDELAAR BONGA ET AL branchial permeability to sodium was even reduced to levels significantly below con trol values (Flik et al, 1989). This decrease was associated with a substantial increase in prolactin cell activity.…”

“…Sodium fluxes were determined as recently de scribed in detail (Flik et al, 1989). Briefly, 24N a pro duced by neutron activation of 23N a 2C 0 3 was used as tracer.…”

“…This decrease was associated with a substantial increase in prolactin cell activity. Since the main function of prolactin is the control of the branchial permeability to water and ions, in particular sodium (Hirano, 1986; W e n d e laar , we have inter preted the increased prolactin cell activity in acid water as an appropriate endocrine response for maintaining water and ion bal ance in acid water (Wendelaar Bonga et al, 1987;Flik et al, 1989). W e have evidence that prolactin is also involved in the accli mation to acid water of eels (Wendelaar Bonga and Balm, 1989).…”