AHEART May 47/5

Zheng, Tao, Wenyan Li, Jun Wang, Bella T. Altura, and Burton M. Altura. Sphingomyelinase and ceramide analogs induce contraction and rises in [Ca]i in canine cerebral vascular muscle. Am J Physiol Heart Circ Physiol 278: H1421–H1428, 2000.—Studies were designed to investigate effects of neutral sphingomyelinase (N-SMase) and ceramide analogs as well as phosphorylcholine on vascular tone and Ca21 mobilization in isolated canine cerebral arterial smooth muscle. N-SMase (0.001–0.1 U/ml) provoked a gradual but sustained vasoconstriction of arterial rings in a concentration-related manner that was endothelium independent. Incubation of denuded arterial rings in Ca21-free medium or pretreatment with verapamil in extracellular Ca21 resulted in a reduction of the N-SMase-evoked constriction. Exposure of arterial rings to 1,2-bis(2-aminophenoxy)ethaneN,N,N8,N8-tetraacetic acid (BAPTA)-AM did not, however, result in a reduction of N-SMase-induced constriction. Both staurosporine and bisindolymaleimide I attenuated N-SMaseinduced contractions to 66% and 72% of control, respectively. N-SMase caused gradual and sustained rises in intracellular Ca21 concentration ([Ca]i) in primary cultured cerebral vascular smooth muscle cells. Pretreatment of these cultured cells with nimodipine and verapamil caused a steady decline in N-SMase-induced rises in [Ca]i. Exposure of the cells to Ca21-free solution reversed the [Ca]i-induced rise triggered by N-SMase to the resting baseline. Both C8 and C16 ceramide (1029–1026 M), but not phosphorylcholine, constricted denuded canine arterial rings in a concentration-related manner and elevated [Ca]i. Our results suggest that the sphingomyelinsignaling pathway, via a probable release of ceramide molecules, may play an important role in regulation of cerebral arterial wall tone.