Contribution of Ca2+ influx to carbachol-induced detrusor contraction is different in human urinary bladder compared to pig and mouse.
Carbachol-induced detrusor contractions are mainly mediated via M3 receptor subtype and depend not only on Ca2+ release from the intracellular calcium stores but also on Ca2+ influx via L-type Ca2+ channels. The purpose of this study was to examine the different contributions of Ca2+ influx and Ca2+ release underlying muscarinic receptor-mediated contractions in human, porcine and murine urinary bladder. Detrusor contractions were measured in urothelium-denuded detrusor strips as responses to cumulatively increasing carbachol concentrations, release of intracellular Ca2+ was determined in Chinese hamster ovary cells stably transfected with human muscarinic M3 (hM3) receptors. In human tissue, 1 microM of the L-type Ca2+-channel blocker nifedipine reduced carbachol contractions to 74%, in pig to 18% and in mouse to 27% of pre-drug controls. 2-aminoethoxyphenyl borate (2-APB, 300 microM), which impairs inositol trisphosphate (IP3)-induced release of Ca2+, reduced carbachol responses in human detrusor to 60%, in pig to 35% and in mouse to 20%, whereas block of the Ca2+-induced Ca2+ release with ryanodine had no significant effect on carbachol contractions in all three species. Carbachol-induced release of intracellular Ca2+ in Chinese hamster ovary cells expressing muscarinic hM3 receptors was completely prevented by 100 microM 2-APB. The direct intracellular IP3 receptor antagonist xestospongin C (10 microM) reduced carbachol-stimulated intracellular Ca2+ to 41% of the control value. Blockade of ATP-dependent Ca2+ uptake into intracellular stores with thapsigargin was associated with a concentration-dependent increase of detrusor contraction, but limited on-top contractions with carbachol. In conclusion, carbachol-induced contractions in human, porcine and mouse detrusor depend differently on Ca2+ influx, since potency of nifedipine reducing muscarinic receptor-mediated detrusor contraction is lower in human bladder. On the other hand, slight species differences are also found when inhibiting IP3-induced Ca2+ release and Ca2+ reuptake into intracellular stores. Taken together, our data show considerable species differences between human, porcine and murine detrusor regarding the relative contributions of Ca2+ influx and maybe also carbachol-induced Ca2+ release that could be of relevance when using different animal models.
Wuest
Melinda
M
Department of Pharmacology and Toxicology, Dresden University of Technology, Dresden, Germany. melinda.wuest@tu-dresden.de
Hiller
Nicole
N
Braeter
Manfred
M
Hakenberg
Oliver W
OW
Wirth
Manfred P
MP
Ravens
Ursula
U
D000368:Aged; D000818:Animals; D001896:Boron Compounds / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D020746:Calcium Channels, L-Type / Q000502:physiology; D002217:Carbachol / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D015544:Inositol 1,4,5-Trisphosphate / Q000494:pharmacology; D008297:Male; D051379:Mice; D008875:Middle Aged; D009119:Muscle Contraction / Q000187:drug effects*; D009543:Nifedipine / Q000494:pharmacology; D013045:Species Specificity; D013552:Swine; D019284:Thapsigargin / Q000494:pharmacology; D001743:Urinary Bladder / Q000187:drug effects* / Q000502:physiology
D001896:Boron Compounds; D020746:Calcium Channels, L-Type; D019284:Thapsigargin; D015544:Inositol 1,4,5-Trisphosphate; D002217:Carbachol; C109986:2-aminoethoxydiphenyl borate; D009543:Nifedipine; D002118:Calcium