Cellular Ca2+ dynamics in urinary bladder smooth muscle from transgenic mice overexpressing Na+-ca2+ exchanger

Abstract

The rise of Ca 2+ concentration ([Ca 2+] i) by reducing external Na + in urinary bladder smooth muscle cells (UBSMCs) from transgenic mice overexpressing Na + /Ca 2+ exchanger type- 1.3 (NCX1.3 tg/tg) was about 4 times as large as that in the wild-type (WT). NCX1 protein expression in UB increased about 4-fold in NCX1.3 tg/tg. The Ca 2+ release by caffeine in UBSMCs was comparable between NCX1.3 tg/tg and WT, but [Ca 2+] i decay was faster in NCX1.3 tg/tg. Contractions induced by acetylcholine, 60 mM K +, or electrical stimulation were significantly smaller in UB segments of NCX1.3 tg/tg. NCX worked in Ca 2+ -extrusion mode during these contractions in UBSMCs of both WT and NCX1.3 tg/tg. © 2010 The Japanese Pharmacological Society.