Seasonal variation in plasma lipids, lipoproteins, apolipoprotein A-I and vitellogenin in the freshwater turtle, Chrysemys picta

An analysis of plasma lipids and lipoprotein fractions was performed over t he course of the annual ovarian cycle of the female turtle, Chrysemys picta . Determinations of total plasma triglycerides, cholesterol, vitellogenin a nd apolipoprotein A-I (apoA-I) were made. The lipid and protein composition of the lipoprotein fractions [very low density lipoprotein (VLDL), low den sity lipoprotein (LDL), high density lipoprotein (HDL) and very high densit y lipoprotein (VHDL)] were also observed over the same period. Plasma trigl yceride and vitellogenin levels were significantly increased in the spring preovulatory period and fall recrudescent phase. Total plasma cholesterol l evels were significantly elevated only at the onset of the fall recrudescen t phase and apoA-I levels were highest during the postoviposition/ovarian a rrest phase. The triglyceride content of VLDL was highest in preovulatory a nimals and there were apparent seasonal changes in the expression of apoA-I and apoE of HDL/VHDL. We conclude that the coordinate regulation of lipids and protein contributes to seasonal ovarian growth and clearance of lipids from plasma, both of which are most likely under hormonal control. (C) 200 1 Elsevier Science Inc. All rights reserved.