1. The relationship between the expression of potassium (K+) channels
and the growth properties of cultured vascular smooth muscle cells was
examined. 2. Two groups of cells having different proliferative rates
were cultured from the Wistar-Kyoto rat aorta. One group of cells, de
rived from early passages (3-5), proliferated with a cell doubling tim
e of 2.41 days. A second group of cells, derived from late passages (>
12), proliferated at a higher rate (cell doubling time, 0.61 days). 3.
Exposure of the early passaged cells to endothelin-1 (0.1 mu mol/L) i
nduced membrane depolarization. In contrast, exposure of the late pass
age cells to endothelin-1 (0.1 mu mol/L) evoked a rapid hyperpolarizat
ion. The hyperpolarization in the late passage cells was blocked by ch
arybdotoxin (20 nmol/L), an inhibitor of the large-conductance Calcium
(Ca)-activated K+ channel. 4. The authors conclude that rapidly proli
ferating vascular smooth muscle cells express enhanced activity of Ca-
activated K+ channels causing marked alterations in the electrical pro
perties of the cells. It is therefore suggested that the reported incr
ease in C.-activated K+ channel activity in the aortae of hypertensive
rats is likely to be associated with the increased proliferative abil
ity of the vascular smooth muscle cells.