| Abstract: | The effects of normobaric hyperoxia on both microsomal membrane fluidity and mechanism of phospholipid synthesis in rabbit liver and kidney have been studied. Hyperoxia induces in both organs an impairment of de novo synthesis of glycerolipids which could be due to an inactivation of acyltransferase activities involved in the initial formation of phosphatidic acid. The ability to replace phospholipid fatty acids by reacylation mechanism decreases slightly in the hyperoxic kidney, while it does not change in the hyperoxic liver. Concerning the effect of high arterial pO2 on microsomal membrane fluidity, the hyperoxic liver shows a more fluid environment within the membrane core of microsomes; however, no difference was shown in that of microsomal membrane core of hyperoxic kidney. An insight into the lipid composition of microsomes indicates that liver microsomal membranes have lower cholesterol content and higher unsaturation degree of phospholipid fatty acids, whereas hyperoxic kidney microsomes become more saturated and did not show any difference in their cholesterol content. In both hyperoxic liver and kidney microsomes, phospholipid content decreases in agreement with the depression of phosphatidic acid biosynthesis. These results are discussed in relation to the values of microsomal membrane microviscosity obtained. |
