Alteration of the increase in intracellular [Ca(2+)] in proliferating smooth muscle cells

Proliferation of smooth muscle cells (SMC) has a role in the development of cardiovascular diseases. We investigated the alteration of contractile signals in proliferating SMC by measuring the increase in intracellular [Ca(2+)] to endothelin-1 (ET-1), noradrenaline (NA), or angiotensin II (AgII). We found that the increase in intracellular [Ca(2+)] by NA or ET-1 decreased in proliferating SMC in comparison to growth-arrested SMC. The increase in intracellular [Ca(2+)] by AgII was stable between the cells. Immunoblotting of inositol 1,4,5-trisphosphate receptors (IP(3)Rs) which are responsible for the mobilization of Ca(2+) by those vasoactive substances revealed that expression of IP(3)R type 1 and type 2 was decreased. Expression of IP(3)R type 3 was increased. The altered Ca(2+) signaling by the cell growth might involve the expression of IP(3)R subtypes.