Alteration of the increase in intracellular [Ca2+] in proliferating smoothmuscle cells

Proliferation of smooth muscle cells (SMC) has a role in the development of cardiovascular diseases. We investigated the alteration of contractile sig nals in proliferating SMC by measuring the increase in intracellular [Ca2+] to endothelin-1 (ET-1), noradrenaline (NA), or angiotensin II (AgII). We f ound that the increase in intracellular [Ca2+] by NA or ET-1 decreased in p roliferating SMC in comparison to growth-arrested SMC. The increase in intr acellular [Ca2+] by AgII was stable between the cells. Immunoblotting of in ositol 1,4,5-trisphosphate receptors (IP(3)Rs) which are responsible for th e mobilization of Ca2+ by those vasoactive substances revealed that express ion of IP3R type 1 and type 2 was decreased. Expression of IP3R type 3 was increased. The altered Ca2+ signaling by the cell growth might involve the expression of IP3R subtypes. (C) 1999 Academic Press.