A new criterion in the bioassay of essential fatty acids: the spontaneous swelling of rat liver mitochondria in vitro

The spontaneous swelling in vitro of liver mitochondria from rats deficient in essential fatty acids (EFA) and normal rats is compared using the change in optical density as a criterion. Differences between both groups are observed only if high sucrose concentrations are used for the isolation of the mitochondria. The change in optical density can be described mathematically by the sum of two exponential functions. A correlation is found between the parameters of this function and the dose of sunflower seed oil fed to EFA‐deficient rats, which makes the method useful as a criterion in an EFA bioassay. The EFA activities of several synthetic polyunsaturated fatty acids are compared using either growth rate or mitochondrial swelling as a criterion.