An association between mitochondria and vesicles in smooth muscle.

Two methods are described for measuring the mitochondrion-vesicle association seen by electron-microscopy in thin sections of the guinea-pig taenia coli. Both methods are based on comparisons of the observed distributions with predicted random distributions. It was found in control muscles that mitochondria were consistently nearer to vesicles than corresponding random points. 1 mM ouabain treatment reduced the mitochondrion-vesicle association for mitochondria which were closer to the membrane surface than 130 nm. Quantitative investigation of the freeze-etch structure of the membrane fracture faces is also reported, confirming the observation that membrane particles are more numerous in vesiculated membrane regions of smooth muscle.