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 elasmobranch mitochondria are similar to those of ot her marine fish, there are considerable differences in the fatty acid content of the phospholipids. Specifically, the percentage of saturate d fatty acids is much higher, the polyunsaturated fatty acid content i s much lower and the chain length is shorter than is typical of other non-urea retaining fishes. The tissues of elasmobranch fishes are unus ual in that they contain the chaotropic agent urea at levels that are capable of disrupting the hydrophobic interactions responsible for mem brane integrity. The mitochondrial membrane properties of the elasmobr anch are consistent with those needed to maintain membrane integrity i n the presence of physiological amounts of urea and indicate membrane adaptation to urea.