alpha- and beta-adrenergic receptors in regulation of ionic transport in frog cornea

The effect of catecholamines and adrenergic blocking agents on the transport of Cl- and Na+ of the isolated frog cornea was studied. Cl- transport was stimulated by the three catecholamines tested at 10(-6) to 10(-5) M concentration. The stimulation produced by 10(-6) M epinephrine was partially inhibited by both the alpha-blocker phentolamine and the beta blocker propranolol. The stimulation produced by 10(-6) M isoproterenol was not affected by 10(-5) M phentolamine but was completely prevented by 10(-5) M propranolol. The stimulation produced by 10(-5) M norepinephrine was completely blocked by the 10(-5) M propranolol and partially by 10(-5) M phentolamine. Catecholamines had no effect on the normally small Na+ transport. When the Na+ transport was previously increased by amphotericin B, epinephrine and isoproterenol produced a small and inconsistent stimulatory effect. Norepinephrine was without effect. It is concluded that both alpha- and beta-adrenergic receptors are present in the frog cornea and that the Cl- transport is increased by the stimulation of either receptor. The minimal effect on the Na+ transport further suggests the separation of pathways of the Cl- and Na+ transport in the frog cornea.