Bilirubin levels in subarachnoid clot and effects on canine arterial smooth muscle cells

Abstract

Background and Purpose: Previous studies have suggested that bilirubin is a potential contributor to cerebral vasospasm. The purpose of this investigation was to determine whether bilirubin accrues in subarachnoid clot, whether its vasoconstrictive effect could involve a direct action on arterial smooth muscle cells, and, if so, whether bilirubin affects their Ca2+ uptake. Methods: Subarachnoid clots were analyzed for bilirubin using high-performance liquid chromatogra-phy. The length and 45Ca2+ uptake of vascular smooth muscle cells enzymatically dissociated from canine carotid arteries were measured before and after exposure to bilirubin solution. Additional experiments were conducted on cultured smooth muscle cells from canine basilar artery and on ATP-depleted cardiac myocytes. Results: Mean ± SE bilirubin concentration in experimental clot was 263 ±35.7 µmol/L. Vascular smooth muscle cells exposed to bilirubin showed progressive shortening (P