RAT AORTIC SMOOTH-MUSCLE CELLS EXPRESSING CHARYBDOTOXIN-SENSITIVE POTASSIUM CHANNELS EXHIBIT ENHANCED PROLIFERATIVE RESPONSES

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.