Abstract

Studies of the response of isolated rabbit urinary bladder strips to adrenergic agents indicate the presence of both alpha and beta-adrenergic receptors in bladder smooth muscle. Using [³H]dihydroergocryptine and [³H]dihydroalprenolo1, we characterized the alpha and beta-adrenergic receptors in the base and body of the rabbit urinary bladder. The density of alpha receptors (in femtomoles per milligram of protein) was significantly greater in the bladder base (78 ± 10) than in the body (18 ± 4), whereas the density of beta receptors was significantly more concentrated in the body (96 ± 10) than in the base (42 ± 6). This uneven receptor distribution correlated well with the physiological response of isolated bladder strips to various adrenergic agonists. Methoxamine (an alpha agonist) stimulated contractility to a significantly greater degree in the musculature of the bladder base than in that of the body. Isoproterenol (a beta agonist) more effectively relaxed the bladder body than the bladder base. Epinephrine (alpha and beta agonist) produced a dose-dependent relaxation in the bladder body, whereas the bladder base responded to the same concentrations with a dose-dependent increase in contractility. We conclude from these studies that the greater response of bladder base to alpha-adrenergic agonists and of bladder body to beta-adrenergic agonists results from the predominance of alpha receptors in the bladder base and of beta receptors in the bladder body.