Changes in rat-liver mitochondria during ketosis |
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Authors: | I Mulder S G Van den Bergh |
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Institution: | Laboratory of Veterinary Biochemistry, State University of Utrecht, Biltstraat 172, 3572 BP Utrecht, The Netherlands |
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Abstract: | - 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.
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