Density distribution, characterization and comparative aspects of plasma lipoproteins in the salamander, Pleurodeles...

Blood plasma from a Urodele amphibian, Pleurodeles waltii, has been found to contain very-low density, low-density and high-density lipoproteins (VLDL, LDL and HDL, respectively). HDL and LDL predominated (concentration range 72-114 and 51-101 mg/dl) with lesser quantities of VLDL (23-51 mg/dl). Following isolation by density gradient ultracentrifugation, the physicochemical properties (morphology, particle size, hydrated density, electrophoretic mobility, and chemical composition) of the three major classes resembled, but were not identical with, those of the corresponding fractions in normal human plasma. The protein moieties of VLDL and LDL consisted mainly of polypeptides of high molecular weight (Mr greater than 60,000), which in their solubility were akin to human apo-B; smaller amounts of another protein migrated to the position of human apo-C-III in basic polyacrylamide gels. The major HDL apolipoproteins were of Mr 31,000 and 27,000, with minor amounts of 13,000, 61,000 and 76,000 components; in alkaline, urea-containing polyacrylamide gels, these major proteins migrated faster than the major components (apo-AI and apo-AII) of human HDL. Immunochemically, lipoproteins with pre-beta-, beta- and alpha-mobility were detected in the VLDL, LDL and HDL, respectively. Salamander VLDL and LDL were found to share an antigenic site(s) with the LDL of trout, chicken and guinea-pig, suggesting the presence of an apo-B-like protein. The chemical compositions and immunochemical reactions of salamander lipoproteins indicate that their structure and metabolism resemble that of other amphibia, reptiles and fish rather more closely than that of most mammals and birds.