Vasoactive Response of Isolated Pulpal Arterioles to Endothelin-1

The vasoactive effect of endothelin-1 applied intraluminally or extraluminally was studied in vitro in isolated perfused porcine pulpal arterioles using a microperfusion system. Pulpal arterioles (outer diameter, 94.2 ± 2.8 μm, n = 12) were cannulated and perfused at a constant flow rate in an environment-controlled bath on the stage of an inverted microscope. The vessel diameters were measured online. Both intraluminal and extraluminal application of endothelin-1 (10 −16 M to 10 −8 M) induced dose-dependent constrictions, reaching 82.3 ± 1.7% ( n = 12) and 70.5 ± 1.3% ( n = 12) at 10 −8 M, respectively. Nifedipine reversed endothelin-1–induced constriction dose-dependently at 10 −7 M and above. These data demonstrate that endothelin-1 induces calcium-dependent vasoconstriction in porcine pulpal arterioles, with extraluminal application more potent, which seems to reflect the possible modulation of vascular endothelium in the control of vascular tone.