["The aims of the present study were to assess 1) the effect of 8-C1-cAMP (cyclic-3'-5'-adenosine monophosphate) on vascular smooth muscle cell (VSMC) proliferation in vitro and 2) the efficacy of systemic administration of 8-C1-cAMP on neointimal formation after balloon injury in vivo.", 'Neointimal formation after vascular injury is responsible for restenosis after arterial stenting. Recently, 8-C1-cAMP, a cAMP analogue that induces growth arrest, has been safely administered in phase I studies in humans.', 'The effect of 8-C1-cAMP on cell proliferation was first assessed on SMCs in vitro. To study the effects of cAMP in vivo, balloon injury was performed in 67 rats using a 2F Fogarty balloon catheter.', 'The 8-C1-cAMP markedly inhibited VSMC proliferation in vitro, reduced protein kinase A (PKA) RIalpha subunit expression, and induced PKA RIIbeta subunit expression. In addition, 8-C1-cAMP reduced, in a dose-dependent manner, neointimal area and neointima/media ratio after balloon injury. The proliferative activity, assessed by proliferating nuclear cell antigen immunostaining, revealed a reduction of proliferative activity of VSMCs in vivo in the 8-C1-cAMP group. Moreover, the systemic administration of 8-C1-cAMP did not affect renal function, blood pressure and heart rate.'] Does 8-chloro-cAMP inhibit smooth muscle cell proliferation in vitro and neointima formation induced by balloon injury in vivo?