Effect of ethinyl estradiol treatment on lipoproteins and LCAT activity in aged rats

Sun min Lee, Bhalchandra J. Kudchodkar, Andras G. Lacko

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Abstract

The induction of hepatic lipoprotein (apo B/E) have been investigated in Fischer-344 rats. These studies were aimed to determine the mechanism underlying the previously observed (Lee et al., Mech. Ageing Dev., 61 (1991) 85-98) hypercholesterolemia and the age-related decrease in the fractional rate of endogenous cholesterol esterification. Young (5 months) and aged (22 months) male Fischer-344 rats were treated with pharmacological doses (5 mg/kg per day) of ethinyl estradiol (EE) for 7 days. Reduction of plasma cholesterol (57% in young vs 47% in aged rats) and high density lipoprotein cholesterol (64% in young vs 63% in aged rats) occurred in both groups upon EE treatment. Initial low density lipoprotein levels were very low in the plasma of young rats and consequently were not affected by EE treatment. However, in aged rats, the low density lipoprotein levels were much higher initially and were markedly reduced by EE treatment. (18.0 vs 10.0 mg/dl). Very low density lipoproteins were about the same initially but increased in aged rats and decreased in young rats upon EE treatment. Both the lecithin: cholesterol acyltransferase (LCAT) activity (as determined with a proteoliposome substrate) and the fractional rate (FR) of the endogenous cholesterol esterification decreased in treated animals compared to controls. However, the differences in the FR of the endogenous cholesterol esterification between young and aged rats (observed before treatment) were nearly abolished upon treatment. These data suggest that the previously observed age related decrease in the FR of endogeneous cholesterol esterification is due to the accumulation of apolipoprotein E-rich (apo E) lipoproteins. Furthermore these findings suggest that the decreased removal of the apo E-rich high density lipoprotein (HDL) in aged rats is due to metabolic events other than the decreased ability of aged hepatic cells to express apo B/E receptors.

Original languageEnglish
Pages (from-to)123-131
Number of pages9
JournalMechanisms of Ageing and Development
Volume64
Issue number1-2
DOIs
StatePublished - Jun 1992

Keywords

  • (CE)
  • (CETP)
  • (EE)
  • (FC)
  • (HDL)
  • (LCAT)
  • (LDL)
  • (TC)
  • (TG)
  • (VLDL)
  • Aging
  • Cholesterol
  • Ethyl estradiol
  • Lecithin cholesterol acyltransferase
  • Lipoproteins
  • Plasma LCAT
  • Rats
  • cholesteryl ester
  • choleteryl ester transfer protein
  • ethinyl estradiol
  • free (unesterified) cholesterol
  • high density lipoproteins(s)
  • low density lipoprotein(s)
  • total cholesterol
  • triglyceride
  • very low density lipoprotein(s)

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