Studies on EndothelirHnduced Actions to Rat Aorta and Cultured Aortic Smooth Muscle Cells

Endothelin is one of the most potent vasoconstrictors known to date. The roles, as well as the mechanisms that endothelin plays in hypertensive diseases have absorbed much attention since its discovery. Our work studied the roles of endothelin on the contraction of rat aorta, in vitro, the proliferation and ATP content of cultured vascular smooth muscle cells from rat aorta. Endothelin could induce a dose-dependent contractile action to rat aorta from the concentration of 1.0 to 18.0 nmol/L and the EC₅₀ value was 3.75±0.75nmol/L. Under normal condition, the percentages of proliferative cells （S+G₂M phase） of cultured vascular smooth muscle cells were among 26.3-29.6%; endothelin had a dose-dependent （P＜0.01） and a time-dependent （P＜0.01） proliferative action to cultured vascular smooth cells. 24 hrs after endothelin action, the percentages of proliferative cells separately increased as high as to 40.7% and 45.6% at concentrations of 10.0 and 100.0 pmol/L. 10.0 pmol/L endothelin could induced a temporary increasing （139.05 ±1.11%, P＜0.01） of ATP contents in cultured vascular smooth muscle cells compared with the control group at 10 min after endothelin action, but 20 min after endothelin action, the ATP level drop sharply to 65.25±5.09% （P＜0.01） and at 30 min, the ATP level recovered a little （71.13±4.04%; P＜0.01） but still lower than normal standard. Our results showed that （1） endothelin can induce dose-dependent vasoconstriction of rat aorta; （2） endothelin also has a proliferativer ole to cultured vascular smooth muscle cells; （3） the change of ATP contents implies that endothelin-induced responses of vascular smooth muscle cells are energy-consuming course.