Involvement of SA channels in orienting response of cultured endothelial cells to cyclic stretch

The present work was designed to elucidate the involvement of Ca²⁺-permeable stretch-activated (SA) channels in the orienting response of endothelial cells to uniaxial cyclic stretch. Endothelial cells from human umbilical vein were cultured on an elastic silicone membrane and subjected to uniaxial cyclic stretch (120% in length, 1 Hz). The cells started to change their morphology 15 min after the onset of stretch, and >90% of the cells oriented perpendicularly to the stretch axis after 2 h. Associated with the orienting response, cell elongation proceeded with a slower rate. Both of the orientating and elongating responses were largely inhibited by the removal of external Ca²⁺ or by Gd³⁺, a potent blocker for the SA channel, but not by nifedipine. Intracellular Ca²⁺ concentration ([Ca²⁺]_i) transiently increased in response to uniaxial stretch, and the basal [Ca²⁺]_i gradually increased during cyclic stretch. This Ca²⁺ response was inhibited by the removal of extracellular Ca²⁺ or by the addition of Gd³⁺. These results suggest that stretch-dependent Ca²⁺ influx through SA channels is essential in the stretch-dependent cell orientation and elongation.