DISAPPEARANCE OF SMOOTH-MUSCLE THICK FILAMENTS DURING K+ CONTRACTION

The arrangement of myofilaments in the smooth muscle of guinea pig taenia coli was observed by electron microscopy to be markedly changed more than 30 min after the oneset of K+-induced isometric contraction. During the tonic response the isometric tension gradually increased, nevertheless almost all the thick filaments disappeared from the whole cell, and thin filaments were located only around the submembraneous area. Using the chemically skinned fiber, we confirmed that the thick filaments had disintegrated and that there was a slight decrease in intracellular Mg2+oncentration. © 1979, Japan Society for Cell Biology. All rights reserved. © 1979, Japan Society for Cell Biology. All rights reserved.