Effects of dl-α-tocopherol (VE) and dl-α-tocopherol nicotinate (EN) on plasma membrane structure of fibroblasts were examined by scanning electron microscopy. When fibroblasts derived from biopsy samples of human skin were cultured in Eagle's minimum essential medium, many microvilli and long microspikes were seen on the cell surface. Marked decreases in the number of microvilli and long spikes were found in fibroblasts cultured with the lipoprotein deficient medium. Further, various small pits appeared on the cell surface, suggesting damages of plasma membrane structure. By addition of 15μM of VE or EN to the lipoprotein deficient medium, these damages were protected and many microvilli and spikes were found on the cell surface.
Levels of free cholesterol and cholesterol ester, both C16 and C18 fatty acid ester, decreased in fibroblasts cultured with the lipoprotein deficient medium. Similarly phospholipids levels of the cells decreased. On the other hand, by addition of VE or EN, free cholesterol, cholesterol ester and phospholipids were kept at normal levels. Further, energy metabolism of fibroblasts cultured with the lipoprotein deficient medium was examined. VE and EN relieved the decrease of ATP contents of the cells induced in the lipoprotein deficient medium.
From these results, it is suggested that the damages of plasma membrane of fibroblasts are induced in the lipoprotein deficient medium and cholesterol and phospholipids of the cells are released into the medium. It is considered that VE and EN protect the membrane of the cells against these injuries and maintain cholesterol and phospholipids of the cells at the normal levels, and therefore that VE and EN are vital to keep the plasma membrane structure.
