We have used an isometric force transducer to study contraction of two types of nonmuscle cells in tissue culture. This method permits the quantitative measurement of contractile force generated by cells of defined type under the influence of external agents while allowing detailed morphological observation. Chick embryo fibroblasts (CEF), which form a contractile network inside a collagen matrix, and human umbilical vein endothelial cells (HUVE), which are located in a monolayer on the surface of the collagen matrix, were studied. CEF and HUVE in 10% FCS produce a substantial tension of 4.5 +/- 0.2 x 10(4) dynes/cm2 and 6.1 x 10(4) dynes/cm2, respectively. Both cell types contract when stimulated with thrombin, generating a force per cell cross-sectional area of approximately 10(5) dynes/cm2, a value approximately an order of magnitude less than smooth muscle. The integrity of the actin cytoskeleton is essential for force generation, as disruption of actin microfilaments with cytochalasin D results in a rapid disappearance of force. Intact microtubules appear to reduce isometric force exerted by CEF, as microtubule-disrupting drugs result in increased tension. Contraction by HUVE precedes a dramatic rearrangement of actin microfilaments from a circumferential ring to stress fibers.

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