Properties of serum high-density lipoproteins in the crab, Cancer antennarius Stimpson.

Two classes of high-density lipoprotein (HDL) comprise virtually all the lipoprotein mass in female hemolymph. These lipoproteins have hydrated densities of 1.187 g/ml (HDL3) and 1.112 g/ml (HDL2). A third species (HDL1, density 1.080 g/ml) appeared in ovigerous crabs. The mean annual HDL protein concentration was 109 mg/dl of which 67% was HDL3. HDL proteins of both HDL2 and HDL3 were mostly insoluble in tetramethylurea. Three major components with apparent mol. wts of 185,000, 100,000 and 84,000 daltons were identified by gel electrophoresis in SDS. Amino acid compositions are reported. Electron microscopy indicated that the HDL are polymorphic and discoidal. Similarities in shape and differences in size of HDL3 and HDL2 particles were consistent with their lipid and protein composition. Phospholipids, mostly phosphatidylcholine, were the dominant lipid class (74%); no cholesteryl esters were detected. Palmitic and oleic acids were the major fatty acid components of esterified lipids.