Action of catecholamines and anti-adrenergic drugs on isolated short-circuited frog skin

Abstract

1. 1. Catecholamines (10 −9 to 10 −6 M) increase the short-circuit current (SCC) and potential difference (PD) in isolated frog skin. Isoprenaline ( pD 2 = 9.03) is active at concentrations 60 times lower than those of noradrenaline. The α-anti-adrenergics were ineffective, whilst β-anti-adrenergics inhibited the catecholamine effect. The antagonism was of a competitive type to isoprenaline, much less specific against noradrenaline. 2. 2. The β-anti-adrenergics induced, at high concentrations, a biphasic effect: a transient increase of SCC and a subsequent decrease under the control values. 3. 3. The catecholamines' effect was lowered by removal of Na + from the Ringer's solution and inhibited by the presence of ouabain. 4. 4. These results indicate that the catecholamine action on isolated short-circuited frog skin is a particular type of β-tropic function similar to that regulating lipolysis in adipose tissue. The action mechanism of catecholamines at low concentrations (10 −9 to 10 −7 M, the more interesting from a physiological point of view) is linked with a stimulation of active sodium transport across the skin.