The Effects of Vasopressin, Theophylline and Cyclic 3'‐5'‐adenosine Monophosphate (Cyclic Amp) on Sodium Transport Across the Frog Skin

Abstract

The effects of vasopressin, theophylline and cyclic AMP on sodium transport across isolated frog skin have been studied using 24Na for the measurement of sodium fluxes. Both vasopressin and theophylline produced consistent increases in short-circuit current, sodium influx and efflux, with a reduction in partial resistance of the skin. The same results were obtained with cyclic AMP only when it was combined with small (loses of theophylline which were by themselves ineffective. The similarity of effect of these three compounds on sodium transport mechanisms strengthens the hypothesis that the physiological activity of vasopressin may be mediated by cyclic AIMIP.THE work of Orloff and Handler [1962] has shown that vasopressin (ADH). theophylline and cyclic adenosine 3'-5'-monophosphate (cyclic AMP) increase both the short-circuit current across isolated toad bladder and the permeability to water. More recently Handler, Butcher, Sutherland and Orloff [1965] have demonstrated an increase in the cyclic AMP content of toad bladder treated with vasopressin. They have suggested, therefore, that the antidiuretic action of ADH may be mediated by an increase in the production of cyclic AMP in receptor cells. Theophylline, which mimics the effect of ADH, is thought to inhibit the inactivation of cyclic AMP by tissue phospho-diesterases.From measurements of short-circuit current alone it is impossible to establish the similarity of effect of ADH, theophylline and cyclic AMP on sodium transport mechanisms. Ussing and Zerahn [1951] found that vasopressin increases both the short-circuit current and the net influx of sodium ions through isolated frog skin and that a decrease in resistance to the passage of sodium ions was responsible for this effect.We have extended this work to include measurements of sodium fluxes across isolated frog skin treated with ADH, theophylline and cyclic AMP. METHODThe isolated frog skin preparation [Ussing and Zerahn, 1951] was used. Ventral frog skin was mounted between two Perspex half-cells each filled with 50 ml. frog Ringer solution. With the potential difference across the skin reduced to zero, the current generated by the skin (the short-circuit current) was measured.After a control period of observation, the substances to be tested were added to the bath fluid on either the inside or the outside of the skin and the changes in shortcircuit current recorded.The influx and efflux of 24sodium were measured for each compound. For this purpose approximately 100 ,e. 24sodium as sodium chloride were introduced into the bath fluid on one side of the skin and samples withdrawn from the opposite side to 416

Regulation of sodium absorption by canine tracheal epithelium.

“…These results suggest stimulation ofNa' absorption by alveolar epithelium. Cyclic-AMP mediated stimulation of Na' absorption has also been observed in amphibian urinary bladder and amphibian skin (23)(24)(25). In these epithelia, antidiuretic hormone stimulation of electrogenic Na' absorption is mediated by an increase in cellular levels of cAMP.…”

Effects of amiloride on active sodium transport by the isolated frog skin: evidence concerning site of action

“…This action may be mediated by cyclic AMP (Orloff & Handler, 1962;Baba et al, 1967). The studies reported here show that amiloride may interact competitively with ADH and also with both dibutyryl cyclic AMP and theophylline.…”

Independent action of antidiuretic hormone, theophylline and cyclic 3′,5′‐adenosine monophosphate on cell membrane permeability in frog skin

“…Sodium ions now flow into the cells under a chemical gradient and a reduced electrical gradient. However, theophylline also increases sodium transport in short circuited skins (Baba et al 1967) where sodium ions can move independently of chloride ions. It is clear that separate channels for sodium and chloride ions must exist.…”

“…ADH increases sodium transport and water flow along an osmotic gradient in both of these tissues (Fuhrman & Ussing, 1951;Koefoed-Johnsen & Ussing, 1953;Bentley, 1966). ADH, the cyclic nucleotide and theophylline produce indistinguishable effects on sodium transport in the frog skin and toad bladder (Baba, Smith & Townshend, 1967;Orloff & Handler, 1961, 1964. It is considered that theophylline mimics ADH by preventing the intracellular break-down of cyclic 3',5'-AMP to 5'-AMP by phosphodiesterase (Butcher & Sutherland, 1962).…”