EXCESS MEMBRANE CHOLESTEROL IS NOT RESPONSIBLE FOR METABOLIC AND BIOENERGETIC CHANGES IN AS-30D HEPATOMA MITOCHONDRIA

Using mitochondria isolated from normal rat liver and AS-30D hepatoma in addition to cholesterol-enriched mitochondria, we have evaluated th e ability of membrane cholesterol to induce changes in mitochondrial f unction, specifically, the preferential export of citrate (i.e., trunc ation of the Krebs cycle). Two in vitro cholesterol-enrichment procedu res failed to produce mitochondria with any physiologically significan t increases in free membrane cholesterol. Alternatively, male Wistar r ats were maintained on a 2% cholesterol diet to elevate mitochondrial cholesterol. This treatment resulted in liver mitochondria which conta ined 70% of the cholesterol levels found in AS-30D hepatoma mitochondr ia, yet only minor metabolic and bioenergetic alterations. Subfraction ation of the various mitochondrial preparations revealed that choleste rol was located primarily in outer membranes of both the cholesterol-e nriched and AS-SOD preparations. We therefore conclude that an increas e in membrane cholesterol is not sufficient to induce ''truncation'' o f the citric acid cycle or any other mitochondrial abnormality in tumo r cells. (C) 1994 Academic Press, Inc.