Salt adaptation in Bufo bufo

Abstract

SUMMARY1. The capacity of adaptation of toads (Bufo bufo) to environments of high salinity was studied and the relative importance of skin, kidney and urinary bladder in controlling the balance of water and salt was assessed.2. Toads were kept in NaCl solutions of 20, 50, 110, 150 and 220 mm and studied in their fourth week of adaptation. A group of animals considered as ' control' was kept in wet soil with free access to water. Plasma, ureter urine, and bladder and colon contents were analysed for sodium, potassium, chloride and osmolality, and total body sodium and water were determined. Absorption of water and 22Na through the skin, and water flow and sodium excretion through the ureter, of intact animals was studied. Hydrosmotic water transport through the isolated urinary bladder of 'control' and adapted animals was determined. The effects of pitressin and aldosterone on the water and sodium balance are described.3. The survival rates of toads kept in saline concentrations up to 150 mm were identical to that of 'control' animals, but half of the animals kept in 220 mm died within 4 weeks.4. There is a linear correlation between the sodium concentrations and osmolality of plasma and of the external media.5. The sodium concentration in colon contents rose with rising external concentrations, up to values higher than the values in plasma.6. Sodium concentrations and osmolalities of ureter and bladder urine increased in adapted animals, the values for bladder urine becoming much higher than those for ureter urine in animals adapted to 110, 150 and 220 mM.7. Total body water, as a percentage of total weight was kept within very narrow limits, although the total body sodium increased with adaptation.8. Absorption of water through the skin for the same osmotic gradients was smaller in adapted than in 'control' animals.

Occludin and hydromineral balance inXenopus laevis

“…rectum; Fig. 5D) may allow elevating faecal salt levels to exceed those in serum, as previously observed in Bufo (Ferreira and Smith, 1968;Ferreira and Jesus, 1973). These strategies would be particularly useful because amphibians lack a loop of Henle in the kidney, and are thus unable to produce hyperosmotic urine.…”

“…net flux from serosa to mucosa) (Ferreira and Smith, 1968). Correspondingly, Na + levels in the colon faecal content of amphibia acclimated to saline conditions are significantly elevated relative to FW animals and typically exceed serum Na + levels (Ferreira and Smith, 1968;Ferreira and Jesus, 1973). In the current study, changes in occludin mRNA expression and Na increased permeability) in the anterior intestine in response to BW would permit relatively greater movement of salt and water across this epithelium.…”

Osmoregulation of the cane toad, Bufo marinus, in salt water

“…Although a sodium pump is necessary for the survival of amphibians in fresh water a decrease in its activity when animals are in highly saline environments would place less burden on the kidneys and bladder to excrete excess electrolytes. A decrease in sodium uptake has been shown in several species when acclimated to high salinities (Ferreira and Jesus, 1973;Katz, 1975).…”

“…The most striking is Rana cancrivora which can tolerate an environmental salinity as great as 80% SW (Gordon et al, 1961). Species such as Xenopus laevis, Bufo viridis, Rana temporaria and Bufo bufo are intermediate in their ability to tolerate brackish water while species such as Rana tigerina are incapable of surviving an environmental salinity of 25% SW or above (Romspert, 1976;Katz, 1973;Ackrill et al, 1969;Ferreira and Jesus, 1973;Gordon et al, 1961).…”

A role for endogenous prostaglandins in the short‐circuit current responses to osmolal changes in isolated frog skin

“…The reduction in salt uptake involves changes in aldosterone and neurohypophyseal peptide secretion (see Bentley, 1971). Local changes in the skin, as suggested by , probably also contribute since aldosterone has a reduced effect on sodium transport across the skin of salt-adapted toads (Ferreira & Jesus, 1973) and saline exposure reduces the number of sodium selective sites in the outer barrier of toad skin (Katz, 1975). The precise intermediary step(s) which brings about these local changes in the skin has not been clarified yet.…”