Autoradiographic localisation of ascorbic acid-dependent binding sites for [125I]iodocyanopindolol in guinea-pig trachea.

Light microscopic autoradiography showed that the supposedly beta-adrenoceptor-selective radioligand [125I]iodocyanopindolol (I-CYP) bound to sites in both the guinea-pig tracheal epithelium and smooth muscle that were sensitive to propranolol and isoprenaline. Low levels of binding were associated with sub-epithelial mucosal cells. Ascorbic acid caused a concentration-related increase in total I-CYP binding which was predominantly associated with the sub-epithelial mucosa, was not inhibited by propranolol, and was thus not associated with beta-adrenoceptors.