Contractile effects of some polypeptides on the isolated urinary bladder of guinea-pig, rabbit, and rat.
In isolated detrusor from guinea-pigs and rats substance P (SP) induced concentration-dependent phasic contractions. Rabbit detrusor strips responded to SP with an initial phasic and an ensuing tonic contraction. The concentration-response curve to SP in this preparation had a biphasic appearance. Eledoisin (E) caused contractile responses similar to those of SP when tested on the guinea-pig detrusor. Somatostatin was tested on the rabbit urinary bladder; it caused a concentration-dependent rise in basal tone, but no phasic contraction. The responses to SP and E were not affected by tetrodotoxin or physostigmine. They were only partly inhibited by high concentrations of atropine and the anticholinergic drug PR 197. Noradrenaline and isoprenaline caused a concentration-dependent inhibition of the peptide induced responses in guinea-pig bladder; at high concentrations in the amines this inhibition was almost complete. Indomethacin did not affect the SP induced contractions in the guinea-pig bladder, reduced the responses in the rabbit detrusor, but increased them in the rat bladder. Contractions elicited by SP and E were rapidly diminished or abolished after 30 min. treatment in a calcium-free medium. The responses were also inhibited by the calcium antagonist nifedipine. In guinea-pig preparations depolarized by potassium (127 mM) both SP and E caused a contractile response approximately 20% of that obtained in normal Tyrode solution. It is concluded that SP and E cause contraction of detrusor by a direct effect on the smooth muscle cells, and that this response is dependent on the extracellular calcium concentration. Prostaglandins may be involved in the SP-induced response of the rabbit detrusor.
D000818:Animals; D004600:Eledoisin / Q000494:pharmacology; D005260:Female; D006168:Guinea Pigs; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects*; D010455:Peptides / Q000494:pharmacology*; D011817:Rabbits; D051381:Rats; D011919:Rats, Inbred Strains; D013004:Somatostatin / Q000494:pharmacology; D013045:Species Specificity; D013373:Substance P / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology; D001743:Urinary Bladder / Q000187:drug effects*
D010455:Peptides; D013373:Substance P; D013779:Tetrodotoxin; D013004:Somatostatin; D004600:Eledoisin