STUDIES ON THE MODE OF ACTION OF EXCESS OF VITAMIN A. 8. MITOCHONDRIAL SWELLING

Abstract

Vitamin A alcohol, at a concentration of 35 uM, causes rat-liver mitochondria to swell rapidly; swelling occurs more readily in a KC1 medium than in a sucrose medium. The swelling is temperature-dependent, and the vitamin has little action on mitochondria in the cold. Vitamin A alcohol has less effect on mitochondria from rat spleen and brain than on mitochondria from rat liver and kidney. Bovine plasma albumin (fraction V) inhibits the action of vitamin A alcohol on rat-liver mitochondria; KCN (3 mM) is ineffective in inhibiting mitochondrial swelling caused by the vitamin. Vitamin A1 alcohol and vitamin A2 alcohol are the only compounds of those tested in the vitamin A series that cause rapid mitochondrial swelling at a concentration of 35 [mu]M. The ability of vitamin A to cause mitocondrial swelling is thought to be consistent with the hypothesis that one site of action of the vitamin is within membranes; it is suggested that the presence of the vitamin in optimum quantities may be required for the maintenance of the normal structure and functioning of mitochondria.