Agonist-induced isometric contraction of smooth muscle cell-populated collagen gel fiber.

String-shaped reconstituted smooth muscle (SM) fibers were prepared in rectangular wells by thermal gelation of a mixed solution of collagen and cultured SM cells derived from guinea pig stomach. The cells in the fiber exhibited an elongated spindle shape and were aligned along the long axis. The fiber contracted in response to KCl (140 mM), norepinephrine (NE; 10(-7) M), epinephrine (10(-7) M), phenylephrine (10(-6) M), serotonin (10(-6) M), and histamine (10(-5) M), but not acetylcholine (10(-5) M). Phentolamine (10(-7) M) produced a parallel rightward shift of the NE dose-response curve. Moreover, NE-induced contraction was partially inhibited by nifedipine and completely abolished by the intracellular Ca(2+) chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid acetoxymethyl ester, the myosin light chain kinase inhibitor ML-9, the Rho kinase inhibitor Y-27632, and papaverine. A [(3)H]quinuclidinyl benzilate binding study revealed that the loss of response to acetylcholine was due to the loss of muscarinic receptor expression during culture. The expression of contractile proteins in the fibers was similar to that in cultured SM cells. These results suggest that, although the fiber is not a model for fully differentiated SM, contractile mechanisms are maintained.