Characteristic inhibition of in vitro swelling of purified rat liver mitochondria induced by Ca2+ or thyroxine by feeding rats a low casein diet.

It has been shown previously by the author that the structure of rat liver mitochondria is changed by a low casein diet. In the present experiments, using the free fatty acid producing substances Ca2+ and thyroxine, and the free fatty acid sodium oleate, the influence of a 4% casein diet on the in vitro swelling process of purified rat liver mitochondria was investigated by following the decrease in optical density at 520 nm after addition of one of the swelling agents. Swelling due to hypotonicity was also investigated. Rats were fed the test diets for 80 to 100 days. Mitochondria were purified by washing three times; after each wash the isotonic suspension was centrifuged at 3,000 X g for 6 minutes. The results show that the in vitro swelling of mitochondria induced by Ca2+ or thyroxine was inhibited greatly in the early period of swelling in rats fed a low casein diet. By comparison to this, there was not a notable effect of a low casein diet on the rate of swelling induced by sodium oleate. But in the case of sodium oleate, the values of optical density were always higher in rats fed a low casein diet, and the differences between two groups were always significant. Swelling due to hypotonicity was not affected at all by a low casein diet.