INTRACELLULAR CALCIUM RESPONSE TO DIRECTLY APPLIED MECHANICAL, SHEARING FORCE IN CULTURED VASCULAR ENDOTHELIAL-CELLS

We studied the responses of cultured endothelial cells to mechanical s hearing force directly applied to those cells in vitro to determine ch anges in the concentration of intracellular calcium ion (Ca++), one of the factors that transfers information within the cell. Cultured bovi ne fetal aortic endothelial cells containing the Ca++ fluorescence ind icator, Fura-2, were rubbed with a latex balloon in a specially design ed system, and changes in the fluorescence of Fura-2 caused by this sh ear stimulation were determined by photometric fluorescence microscopy . Immediately after shear stimulation, the concentration of Ca++ in th e cells was increased and reached a peak (511 +/- 165 nM, n = 12) with in 15 seconds after stimulation. after the peak, the concentration was gradually restored to the resting level (55 +/- 17 nM, n = 12). The m agnitude of the Ca++ response was dependent on the intensity of the sh ear force applied. Analysis of fluorescence images of Fura-2 revealed that the eels showed this Ca++ reaction without being injured or desqu amated, although there were slight differences in the degree and durat ion of reaction among cells. This reaction appeared even when the cell s were placed in the air with no contact with the fluid. This result s uggests that neither the fluid flow associated with the balloon moveme nt nor chemical substances in the fluid are involved in the reaction, but that pure physical force alone is responsible for the Ca++ reactio n. Further, it suggests that endothelial cells have the ability to per ceive such physical stimulation as shear force and to transfer this in formation to the interior of the cell via changes in the intracellular Ca++ concentration.