Comparison of liver mitochondrial membranes from an agnathan (Myxine glutinosa), an elasmobranch (Raja erinacea) and a teleost fish (Pleuronectes americanus)

The membranes of elasmobranch liver mitochondria differ substantially from those of other marine fish. Although the proportions of the major phospholipids in clasmobranch mitochondria are similar to those of other marine fish, there are considerable differences in the fatty acid content of the phospholipids. Specifically, the percentage of saturated fatty acids is much higher, the polyunsaturated fatty acid content is much lower and the chain length is shorter than is typical of other non-urea retaining fishes. The tissues of elasmobranch fishes are unusual in that they contain the chaotropic agent urea at levels that are capable of disrupting the hydrophobic interactions responsible for membrane integrity. The mitochondrial membrane properties of the elasmobranch are consistent with those needed to maintain membrane integrity in the presence of physiological amounts of urea and indicate membrane adaptation to urea.