Dependency of detrusor contractions on calcium sensitization and calcium entry through LOE-908-sensitive channels.
1. The subcellular mechanisms regulating stimulus-contraction coupling in detrusor remain to be determined. We used Ca(2+)-free solutions, Ca(2+) channel blockers, cyclopiazonic acid (CPA), and RhoA kinase (ROK) inhibitors to test the hypothesis that Ca(2+) influx and Ca(2+) sensitization play primary roles. 2. In rabbit detrusor, peak bethanechol (BE)-induced force was inhibited 90% by incubation for 3 min in a Ca(2+)-free solution. By comparison, a 20 min incubation of rabbit femoral artery in a Ca(2+)-free solution reduced receptor-induced force by only 5%. 3. In detrusor, inhibition of sarcoplasmic reticular (SR) Ca(2+) release by 2APB, or depletion of SR Ca(2+) by CPA, inhibited BE-induced force by only 27%. The CPA-insensitive force was abolished by LaCl3. By comparison, 2APB inhibited receptor-induced force in rabbit femoral artery by 71%. 4. In the presence of the non-selective cation channel (NSCC) inhibitor, LOE-908, BE did not produce an increase in [Ca(2+)]i but did produce weak increases in myosin phosphorylation and force. 5. Inhibitors of ROK-induced Ca(2+) sensitization, HA-1077 and Y-27632, inhibited BE-induced force by approximately 50%, and in combination with LOE-908, nearly abolished force. 6. These data suggest that two principal muscarinic receptor-stimulated detrusor contractile mechanisms include NSCC activation, that elevates [Ca(2+)]i and ROK activation, that sensitizes cross bridges to Ca(2+).
Jezior
J R
JR
Department of Urology, Eastern Virginia Medical School, PO Box 1980, Norfolk, Virginia, VA 23501, USA.
Brady
J D
JD
Rosenstein
D I
DI
McCammon
K A
KA
Miner
A S
AS
Ratz
P H
PH
D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine / Q000031:analogs & derivatives* / Q000494:pharmacology; D000081:Acetamides / Q000494:pharmacology*; D000577:Amides / Q000494:pharmacology; D000818:Animals; D018723:Bethanechol / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005260:Female; D007093:Imidazoles / Q000494:pharmacology; D066298:In Vitro Techniques; D007211:Indoles / Q000494:pharmacology; D007473:Ion Channels / Q000187:drug effects* / Q000502:physiology; D007546:Isoquinolines / Q000494:pharmacology*; D009119:Muscle Contraction / Q000187:drug effects*; D018994:Myosin Light Chains / Q000187:drug effects / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D047428:Protein Kinase Inhibitors; D011725:Pyridines / Q000494:pharmacology; D011817:Rabbits; D013997:Time Factors; D001743:Urinary Bladder / Q000187:drug effects* / Q000502:physiology; D014700:Verapamil / Q000494:pharmacology
D000081:Acetamides; D000577:Amides; D002121:Calcium Channel Blockers; D007093:Imidazoles; D007211:Indoles; D007473:Ion Channels; D007546:Isoquinolines; D018994:Myosin Light Chains; D047428:Protein Kinase Inhibitors; D011725:Pyridines; D018723:Bethanechol; C108830:Y 27632; C081356:LOE 908; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D014700:Verapamil; C063159:1-(2-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenylethyl)-1H-imidazole; C049347:fasudil; D002118:Calcium; C000543:cyclopiazonic acid