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Am J Vet Res. 2003 Aug;64(8):1052-8.

Effect of hypothyroidism on kinetics of metabolism of very-low-density lipoprotein in mares.

Author information

  • 1Department of Veterinary Clinical Sciences, School of Veterinary Medicine, School of Agriculture, Purdue University, West Lafayette, IN 47907-1248, USA.

Abstract

OBJECTIVE:

To compare kinetics of the metabolism of very-low-density lipoprotein (VLDL) apolipoprotein B (apoB) before and after thyroidectomy in mares.

ANIMALS:

5 healthy adult mares.

PROCEDURE:

Thyroidectomy was performed in euthyroid mares. Kinetics of VLDL apoB metabolism were measured before and after thyroidectomy by use of a bolus IV injection of 5,5,5-2H3 (98%) leucine (5 mg/kg) and subsequent isolation of labeled amino acid from plasma and VLDL. Labeled leucine was quantified by use of gas chromatography-mass spectrometry. Production rate (PR), delay time, and fractional catabolic rate (FCR) were calculated for the 2 forms of equine VLDL, apoB-48 VLDL, and apoB-100 VLDL. Plasma lipid concentrations were measured, and VLDL composition was determined.

RESULTS:

Physical appearance of horses was not altered by thyroidectomy. Significantly lower mean blood concentrations of thyroid hormones and non-esterified fatty acids were detected following thyroidectomy. Mean percentage of free cholesterol in VLDL was significantly higher after thyroidectomy. Mean plasma VLDL concentration or kinetics of apoB-48 or apoB-100 were not significantly altered by thyroidectomy. Mean +/- SEM PR was significantly lower (8.70 +/- 1.61 mg/kg/d) and mean delay time significantly longer (1.58 +/- 0.12 hours) for apoB-48 VLDL in euthyroid mares, compared with values for thyroidectomized mares (16.15 +/- 2.24 mg/kg/d and 0.93 +/- 0.10 hours, respectively).

CONCLUSIONS AND CLINICAL RELEVANCE:

Hypothyroidism did not significantly alter plasma VLDL concentrations or kinetics of VLDL apoB metabolism. Metabolism of apoB-48 VLDL differed significantly from that of apoB-100 VLDL in euthyroid mares.

PMID:
12926601
[PubMed - indexed for MEDLINE]
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