Studies on isolated smooth muscle cells. VII. Response to agonists and the contraction velocity of taenia coli of guinea pig and the single smooth muscle cells.

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Abstract
Single smooth muscle cells were isolated from tenia coli of guinea pigs and degrees of responses of acetylcholine, histamine and prostaglandin E2 and velocity of acetylcholine-contraction were compared with those of whole tissue. The contraction of single cells by these agonists were dose-dependent and ED50 of acetylcholine, histamine and prostaglandin E2 were 0.3-1.1 .times. 10-6, 5-11 .times. 10-7 and 1-3 .times. 10-9 M, respectively. These values were quite similar to those obtained with whole tissue. It took 2.0 .+-. 0.2 s for the single cells to be contracted completely by 10-4 M acetylcholine while it took 6.9 .+-. 0.2 s for the isotonic contraction of whole tissue. Times for a half maximum contraction, assuming that the whole tissue and the single cells were contracted at the maximum velocity, were 1.43 .+-. 0.05 and 0.92 .+-. 0.12 s, respectively, when 10-4 M acetylcholine was applied. Response of muscle cells in the tissue to agonists was reflected on magnitude of the contraction of whole tissue. Pharmacological properties of smooth muscle cells of tenia coli were apparently not changed during the isolation procedure, whereas contraction velocity of single cells was faster than that of whole tissue. Reasons for the difference in velocity were discussed.

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