AJP - Regulatory, Integrative and Comparative Physiology, Vol 260, Issue 5 911-R915, Copyright © 1991 by American Physiological Society
Evidence that beta 2-receptors mediate action of catecholamines on endolymphatic sac DC potential
N. Mori and N. Uozumi
Department of Otolaryngology, Kagawa Medical School, Japan.
Our recent study has revealed that catecholamines depress the endolymphatic
sac direct current potential (ESP) by the beta-adrenergic action [Mori et
al., Am. J. Physiol. 259 (regulatory Integrative Comp. Physiol. 28):
R921-R924, 1990]. Beta-Adrenergic receptors have been subclassified into
beta 1- and beta 2-receptors. Using beta 1-selective (dobutamine) and beta
2-selective (salbutamol) agonists and a beta 1-selective antagonist
(atenolol), we determined the subtype of beta-adrenergic receptors that
mediate the action of catecholamines on the ESP. Salbutamol depressed the
ESP to a larger degree than dobutamine [34.0 +/- 2.6 (n = 7) vs. 13.0 +/-
2.0% (n = 8)] with a much lower dose (100 vs. 1,000 micrograms/kg).
Atenolol failed to block the action of salbutamol on the ESP at a dose of 1
mg/kg, whereas propranolol inhibited it at the same dose. The results
indicate that beta 2-receptors mediate the action of catecholamines on the
ESP.
