ATP induced-relaxation in the mouse bladder smooth muscle.
1. The effect of adenosine 5'-triphosphate (ATP) on the free cytosolic Ca2+ concentration ([Ca2+]i) as measured with the fluorescent Ca(2+)-indicator fura-2, and on force was investigated in the intact smooth muscle strips of the mouse urinary bladder. 2. ATP elicited, when exogenously applied, a large increase of [Ca2+]i with limited force development resulting in a marked Ca(2+)-force dissociation. 3. Release of endogenous neurotransmitters by transmural electrical stimulation (TES) for 30 s induced a steady increase of [Ca2+]i and a peak contraction, followed within 15 s by a relaxation. 4. In carbachol-prestimulated preparations, ATP elicited an initial rise of [Ca2+]i followed by a return to the initial precontraction Ca(2+)-level. Force in contrast presented a biphasic pattern, i.e. an initial contraction was followed by a sustained relaxation. 5. In the K(+)-depolarized precontracted preparation, ATP elicited a slight initial rise of [Ca2+]i. The partial relaxation of the force during depolarization was not preceded by a transient contraction. 6. The ATP-induced relaxation of the K(+)-prestimulated preparations was not inhibited by 8-phenyltheophylline, a potent P1-purinoceptor antagonist. 7. The order of potency for relaxation of the ATP analogues was 2-MeSATP > ATP > beta gamma Me-ATP, which is characteristic for P2y-purinoceptors. 8. These results indicate that, besides its activating effect, ATP also relaxes the mouse urinary bladder. It is suggested that the relaxant effect, mediated through P2y-purinoceptors, is mainly responsible for the low contractile potency of ATP in the bladder.
Boland
B
B
Department of Physiology, U. C. Louvain, Bruxelles, Belgium.
Himpens
B
B
Paques
C
C
Casteels
R
R
Gillis
J M
JM
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D004558:Electric Stimulation; D016257:Fura-2; D066298:In Vitro Techniques; D008297:Male; D051379:Mice; D009119:Muscle Contraction / Q000187:drug effects; D009126:Muscle Relaxation / Q000187:drug effects / Q000502:physiology; D009130:Muscle, Smooth / Q000187:drug effects* / Q000502:physiology; D018377:Neurotransmitter Agents / Q000378:metabolism; D011983:Receptors, Purinergic / Q000187:drug effects; D013806:Theophylline / Q000031:analogs & derivatives / Q000494:pharmacology; D001743:Urinary Bladder / Q000166:cytology / Q000187:drug effects
D018377:Neurotransmitter Agents; D011983:Receptors, Purinergic; D000255:Adenosine Triphosphate; D013806:Theophylline; C028322:8-phenyltheophylline; D002118:Calcium; D016257:Fura-2