The effects of monensin on membrane lipids of cultured human skin fibroblasts.

We have investigated the effects of monensin, a monovalent cationophore, on the metabolism of neutral lipids, fatty acids, ceramide and phospholipids in cultured human skin fibroblasts. Treatment with 1 microM monensin for 18 h reduced the cellular cholesterol ester content to less than one-third of untreated cells, and incorporation of [3H]acetate into cholesterol ester was also reduced, to less than one-fifth. Concomitantly, a greater conversion of [3H]acetate into free cholesterol occurred. There was a moderate increase in free fatty acids, but no change in triacylglycerol content, although the content of the latter appeared to increase in the presence of fetal calf serum in the culture medium. Phosphatidylcholine decreased in content and phosphatidylserine increased among the phosphatides, but ceramide remained unchanged after monensin treatment. These findings suggest that monensin influences the metabolic interrelationships of structural lipids in fibroblasts.