BETA-AGONISTS AND SECRETORY-CELL NUMBER AND INTRACELLULAR GLYCOPROTEIN IN AIRWAY EPITHELIUM - EFFECT OF ISOPROTERENOL AND SALBUTAMOL

Abstract

The effect of systemic administration of the .beta.-adrenergic agonists isoproterenol and salbutamol on the secretory cell populations in 7 regions of rat airway epithelium (3 extrapulmonary and 4 intrapulmonary) and on the size of salivary glands and heart is described. Isoproterenol (a nonselective .beta.-adrenergic agonist) significantly increases secretory cell number in all airway regions except the midtrachea; salbutamol (a selective .beta.2 agonist) increases secretory cell number only in proximal and peripheral regions. The absolute number of secretory cells is greatest in the most peripheral region after isoproterenol administration and in the most proximal region after salbutamol; but both drugs produce the greatest relative increase at the periphery. In proximal and peripheral regions the increase by isoproterenol (< 3- and 14-fold, respectively) is greater than by salbutamol (< 2- and 3-fold, respectively). In all airway regions both drugs modify intracellular glycoprotein in the secretory cell population; within a given region modification is much the same. In the most proximal region the population of cells synthesizing only granules of neutral glycoprotein significantly increases; in other regions increase is in cells synthesizing only granules of acid. A significant shift in glycoprotein synthesis occurs whether or not the secretory cell population is increased; existing and newly appearing cells apparently modify their product. Isoproterenol significantly increases the size of the parotid and submaxillary glands; salbutamol increases the size of the parotid only. Isoproterenol significantly increases the weight of both ventricles of the heart; salbutamol has no such effect.