Effect of prolonged saline‐exposure on sodium transport across frog‐skin

Abstract

SUMMARY1. Differences in Na transport between skins from Rana temporaria and R. esculenta maintained for up to several weeks in water or 0 7 % saline (0-7 g NaCl in 100 ml. H20), with and without daily injections of 4% saline (4 g NaCl in 100 ml. H20), were measured, in vitro.2. In saline-treated skins, the following changes were found: (a) An increased Na content. (d) A highly significant fall in Na influx, accounting for the reduced I8C; a small reduction in Na efflux was not significant, statistically.(e) The Pitressin-induced increment in I., was usually considerably lower compared with that in water-exposed skins; considered relative to the pre-Pitressin values, however, there were no clear differences.(f) By calculation from the changes in resistance (R) caused by replacement of outer Na2SO4 Ringer by K2S04 Ringer solution, I. Eo, the electromotive force of the active sodium transport system, was moderately, but significantly, reduced, II. R shuntt the shunt path resistance, was moderately, but significantly, increased, and III. Rser' the series path resistance, was considerably, and highly significantly, increased.(g) K influx from outer K2SO4 Ringer solution was reduced. 3. Differences between skins from water-exposed and saline-treated frogs persisted, in vitro, despite the occurrence of anionic-dependent acute changes after mounting in Ringer solution.4. There were seasonal changes in 1,, and in the effects of saline treatment.R. HORNB Y AND S. THOMAS 5. The findings are discussed in terms of decreased permeability of outer barriers to ion-diffusion, and reduced activity of a Na pump.

Salt‐induced changes in sodium transport across the skin of the euryhaline toad, Bufo viridis.

“…Similar variations have been noted by other investigators (Maetz et al 1958;Hong, Park, Park & Kim, 1968;Hornby & Thomas, 1969;and others). Care was taken, however, to run all experimental groups at a time, to minimize for the variations.…”

“…Although considerable variations (both seasonal and among batches) have been recorded in the electrical properties of the skin (Table 5, and Katz, 1973b), skins from salt-adapted toads appeared to be consistently different from skins which were taken from distilled-water-adapted toads. Similar variations have been noted by other investigators (Maetz et al 1958;Hong, Park, Park & Kim, 1968;Hornby & Thomas, 1969;and others). Care was taken, however, to run all experimental groups at a time, to minimize for the variations.…”

“…However, although this contention may hold for shortterm adaptation, it cannot explain the changes reported here, where these hormones could not change the basic differences which persisted among the various groups of adaptation. The same conclusion should apply to the experiments of Hornby & Thomas (1969). Similarly, it was found in in vivo experiments that Na uptake in salt-adapted toads remained considerably below that of animals which were kept in tap water, even after injection of supramaximal doses of aldosterone (Ferreira & Jesus, 1973;Katz, 1973b).…”

“…Na transport across amphibian skin is reduced after a few days under saline conditions (Maetz, Jard & Morel, 1958;Crabb6, 1963;Hornby & Thomas, 1969). We have taken advantage of the resistance of Bufo viridis to high external salinity to study the mechanism of the reduction in Na transport across the skin, which follows long-term adaptation to high salinities.…”

Direct current electric field in some teleost species: Effect of medium salinity

“…In this case, in marine fish whose isolated skin is capable of changing the polarity of the transepithelial potential difference with varying sodium concentrations in the bathing solutions, the sign of the potentials in the field surface changes when the fish are transferred from salt water to fresh water and vice versa. On the other hand, in freshwater fish and frogs whose isolated skin does not change the polarity of the potential difference and the direction of active ion transport (Tercafs and Schoffeniels 1966;Hornby and Thomas 1969), the sign of the potentials on the body surface does not change when the fish or frogs are transferred from fresh water to salt water.…”