Effects of active peptides on the isolated muscle of the human urinary bladder.

We studied the effect of 29 active peptides, six biogenic amines, and two prostaglandins on isolated preparations of the longitudinal muscle of the human urinary bladder. The peptide that had the most potent stimulant action was angiotensin II, followed by eledoisin and kassinin (substance P-like peptides), and by bombesin and litorin. The threshold dose of angiotensin was frequently as low as 0.3 to 0.5 ng per ml. Eledoisin showed approximately 10 per cent of the activity of angiotensin II. All peptides had a direct stimulant effect on vesical smooth muscle. Further studies are required to determine if angiotensin and/or substance P-like peptides are involved in the control of motility of the human urinary bladder, as constituents of the secretion of peptidergic nerves.