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First published online March 2, 2007
Journal of Experimental Biology 210, 1064-1074 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.02724

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Characterization of very-low density lipoprotein particle diameter dynamics in relation to egg production in a passerine bird

Katrina G. Salvante^1,*, Gina Lin², Rosemary L. Walzem² and Tony D. Williams¹

¹ Department of Biological Sciences, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia, V5A 1S6, Canada
² Poultry Science Department, Texas A&M University, College Station, TX 77843, USA

^* Author for correspondence at present address: Department of Biology, Coker Hall, CB 3280, University of North Carolina–Chapel Hill, Chapel Hill, NC 27599-3280, USA (e-mail: ksalvante{at}unc.edu)

Accepted 16 January 2007

During avian egg production, oestrogen mediates marked increases in hepatic lipid production and changes in the diameter of assembled very-low density lipoprotein (VLDL). A nearly complete shift from generic VLDL (70 nm in diameter), which transports lipids to peripheral tissues, to yolk-targeted VLDL (VLDLy) (30 nm), which supplies the yolk with energy-rich lipid, has been observed in the plasma of laying domestic fowl. We validated an established dynamic laser scattering technique for a passerine songbird Taeniopygia guttata, the zebra finch, to characterize the dynamics of VLDL particle diameter distribution in relation to egg production. We predicted that non-gallinaceous avian species that have not been selected for maximum egg production would exhibit less dramatic shifts in lipid metabolism during egg production. As predicted, there was considerable overlap between the VLDL particle diameter distributions of laying and non-laying zebra finches. But unexpectedly, non-laying zebra finches had VLDL diameter distributions that peaked at small particles and had relatively few large VLDL particles. As a result, laying zebra finches, in comparison, had diameter distributions that were shifted towards larger VLDL particles. Nevertheless, laying zebra finches, like laying chickens, had larger proportions of particles within proposed VLDLy particle diameter ranges than non-laying zebra finches (e.g. sVLDLy: 50% vs 37%). Furthermore, zebra finches and chickens had similar modal (29.7 nm in both species) and median (32.7 nm vs 29.6 nm) VLDL particle diameters during egg production. Therefore, although zebra finches and chickens exhibited opposing directional shifts in VLDL particle diameter distribution during egg production, the modifications to VLDL particle structure in both species resulted in the realization of a common goal, i.e. to produce and maintain a large proportion of small VLDL particles of specific diameters that are capable of being incorporated into newly forming egg yolks.)

Key words: VLDL, yolk-targeted VLDL, reproduction, VLDL particle diameter, zebra finch

This article has been cited by other articles:

				K. G. Salvante, R. L. Walzem, and T. D. Williams What comes first, the zebra finch or the egg: temperature-dependent reproductive, physiological and behavioural plasticity in egg-laying zebra finches J. Exp. Biol., April 15, 2007; 210(8): 1325 - 1334. [Abstract] [Full Text] [PDF]