Mitochondrial swelling at acid pH.

Abstract

The effect of variations of pH on swelling of rat liver mitochondria was studied.It was found that mitochondria swell at acid pH (5.0–6.0) when they are incubated in isotonic solution of potassium chloride. The extent of swelling increased with decreasing tonicity of the medium. However, mitochondria did not swell at acid pH when they were incubated in isotonic sucrose. The inhibitory effect of sucrose was partially released by the addition of electrolytes to the medium.When unbuffered suspensions of mitochondria with different pH values were prepared by the addition of hydrochloric acid or sodium hydroxide to the incubation medium, it was observed that the extent of swelling increased both with acidity (6.0 to 5.0) and with alkalinity (7.0 to 8.0).Titration of the unbuffered mitochondrial suspensions showed a maximum buffering capacity in the ranges of pH values where maximum rate of swelling occurred.These results suggest that the mitochondrion behaves as a combination of osmometer and protein gel.