Density-dependent hyperpolarization in cultured aortic smooth muscle cells.

The membrane potential (Em) of cultured aortic smooth muscle cells from Sprague-Dawley (SD), Wistar-Kyoto (WKY), and spontaneously hypertensive (SHR) rats was measured in proliferating primary cultures. Em of SD cells in high-density cultures was -51 to -58 mV, whereas that of low-density cultures (1-2 days) was -30 mV. This difference was due to a continuous process of hyperpolarization during proliferation in culture. Em of WKY and SHR hyperpolarized similarly, from -12 to -42 and -38 mV, respectively. Hyperpolarization of Em of SD, WKY, and SHR cells was related to cell density rather than time in culture. Em may be a sensitive and significant indicator of the changes in the differentiated state expressed by proliferating smooth muscle in vitro.