Molecular Pharmacology, Vol 19, 525-528, Copyright © 1981 by the American Society for Pharmacology and Experimental Therapeutics

Effect of Adenosine Triphosphate on Contractility and Adenosine Triphosphatase Activity of the Rabbit Urinary Bladder

¹ Division of Urology, Department of Surgery, University of Pennsylvania School of Medicine and the Veterans Administration Medical Center, Philadelphia, Pennsylvania 19104

There is circumstantial evidence that ATP may be an excitatory neurohumoral transmitter in the urinary bladder of several species. Muscle bath studies in vitro demonstrated that exogenously applied ATP can produce a dose-dependent contraction of the rabbit urinary bladder. These studies indicate that the concentrations of ATP necessary to stimulate bladder contraction are significantly greater than one would expect if ATP were acting through a neurohumoral receptor system. The purpose of our study was to compare the contractile action of ATP on isolated strips of urinary bladder with the ATP hydrolysis activity of these strips. The results from these studies demonstrate that, over the time course of the contractile effect of ATP, less than 0.1% of the ATP present in the bath is hydrolyzed by the tissue. Thus, the requirement for high concentrations of ATP for contractile stimulation cannot be ascribed to ATP hydrolysis by the tissue. Additionally, it is interesting to note that ,-methylene ATP was approximately 100 times as potent as disodium ATP in its ability to stimulate contraction in the rabbit urinary tract. This difference in potency is probably a function of the structure of ,-methylene ATP rather than its resistance to hydrolysis by ATPase.