The effect of osmotic pressure on the activity of Carcinus maenas mitochondria

Abstract

1. 1. Mitochondria were isolated from the hepatopancreas of the crab Carcinus maenas at 0.25 M sucrose solution (preparation A) and at 0.8 M (preparation B). 2. 2. The crab osmoregulates in 20–80 per cent sea water but does not regulate over the range 80–100 per cent sea water. 3. 3. The physiological in vivo concentration of the intracellular fluid in animals kept in 80 per cent sea water is equivalent to 0.8 M sucrose. 4. 4. The succinic oxidase activity is higher in mitochondria from preparation A than preparation B. 5. 5. Preparation A has its peak succinic oxidase activity at 0.3 M assay medium concentration. Preparation B has its peak activity at 0.6 M. 6. 6. Mitochondria from preparation A behave as osmometers below 0.4 M whilst those from preparation B behave as osmometers below 1.0 M. 7. 7. It is suggested that the increase in respiration rate of mitochondria when the medium is diluted and the mitochondria swell may help explain the observed respiration-osmoregulation changes in the intact animal, and may be part of a feedback control system.