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).