Two-step consumption of yolk granules during the development of quail embryos
Article first published online: 17 JUN 2004
Development, Growth & Differentiation
Volume 46, Issue 3, pages 229–238, April 2004
How to Cite
Yoshizaki, N., Soga, M., Ito, Y., Mao, K. M., Sultana, F. and Yonezawa, S. (2004), Two-step consumption of yolk granules during the development of quail embryos. Development, Growth & Differentiation, 46: 229–238. doi: 10.1111/j.1440-169X.2004.00740.x
- Issue published online: 17 JUN 2004
- Article first published online: 17 JUN 2004
- Received 26 January 2004; revised 26 February 2004; accepted 27 February 2004.
- cathepsin D;
- salt concentration;
- yolk consumption;
- yolk granule
The mechanism of yolk consumption was studied morphologically and biochemically in Japanese quail Coturnix japonica. The amount of yolk granules in the yolk (or ‘yolk cell’) decreased in two steps during embryonic development. In the first step, during days 0–4 of incubation, the yolk-granule weight decreased at a rate of 13 mg/day. This decrease was due to segregation by endodermal cells that were newly formed in the developing yolk sac. In the second step after day 6, the decrease was drastic at a rate of 29.8 mg/day during days 6–12 and very slow thereafter. The decrease at the second step was due to the enzymatic digestion of yolk granules by cathepsin D that coexisted in yolk spheres. This digesting reaction was triggered by the solubilization of the granules with high concentrations of salts that were supplied after disruption of the limiting membrane of yolk spheres. The ‘yolk cell’ seemed to die around day 5 of incubation. Thus the digestion products might be taken up together with yolk lipids by endocytosis into the endodermal cells and transported to blood vessels.