The Role of High-Density Lipoproteinsin Maintaining Osmotic Homeostasis in the Goldfish Carassius auratus L. (Cyprinidae)

A hypothesis on the involvement of high-density lipoproteins (HDL) in maintaining osmotic homeostasis in fish was proposed. For its verification, structural reorganizations of serum HDL in the goldfish Carassius auratus L. were investigated under natural conditions (during the seasonal dynamics) and in experiments on the effect of critical salinity. A common algorithm of HDL rearrangements in wild freshwater fish and those acclimated experimentally to critical salinity was established. It consists in reversible dissociation–association of HDL particles. In the natural (freshwater) habitat, this algorithm is congruent with the dynamics of total protein distribution across the capillary wall, while under experimental conditions with changes in water salinity. These findings imply the possibility of multiple strategies of maintaining osmotic homeostasis with the involvement of HDL in higher teleosts the blood of which, in contrast to mammals, lacks a specialized osmotically active protein albumin. The role of HDL as universal metabolic regulators and stabilizers is discussed.