Changes in rat-liver mitochondria during ketosis

• 1.1. Disruption of rat-liver mitochondria by repeated freezing and thawing solubilizes less protein than treatment of the mitochondria with an ultrasonic disintegrator or with a detergent (Triton).
• 2.2. After centrifugation of the disrupted mitochondria, the activity of the 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) pathway is recovered in the pellet if the disruption occurred by freezing and thawing, whereas it is in the supernatant after Triton treatment.
• 3.3. After sonication, the 2 enzymes of the HMG-CoA pathway are largely separated over pellet and supernatant.
• 4.4. Freezing and thawing solubilizes more protein from liver mitochondria from ketotic than from normal rats.
• 5.5. Mitochondria from normal rats need a longer sonication for full expression of the activity of the HMG-CoA pathway than mitochondria from ketotic rats.
• 6.6. It is concluded that mitochondria from ketotic rats are more fragile than those from normal rats.
• 7.7. The increased activity of the HMG-CoA pathway, previously observed in frozen mitochondria from ketotic rats. has to be ascribed to the greater fragility of these mitochondria.
• 8.8. The activity of the HMG-CoA pathway is inhibited by ATP and stimulated by calcium ions. The latter effect is only observed if the mitochondria are disrupted by freezing and thawing.
• 9.9. In the presence of calcium ions frozen mitochondria from ketotic and normal rats have the same high activity of the HMG-CoA pathway.
• 10.10. The mechanism and the possible function of this calcium effect in vivo are discussed.