Immunoelectron microscopical demonstration of egg-yolk plasma precursor vitellogenin in the hepatocyte of oestradiol-treated cockerels.

Vitellogenin has been localized at the electron microscopical level in the liver of the cockerel using a colloidal gold technique. White leghorn cockerels were treated with 17 beta-oestradiol to induce vitellogenesis. Pieces of liver were removed from control and experimental birds on the 4th and 8th days following hormone treatment, and embedded in Lowicryl K4M. Vitellogenin was isolated from the plasma of oestradiol-treated cockerels, and the antibody to it elicited in rabbits and made vitellogenin-specific by affinity chromatography on lipovitellin-Sepharose columns. At the light microscopical level, the intensity of immunohistochemical staining was considerably above background levels in oestradiol-treated cockerels. At the electron microscopical level, gold particles indicating antigenic sites of vitellogenin were largely confined to the rough endoplasmic reticulum, Golgi apparatus, immature and lysosomes and phagosomes within hepatocytes and sinusoidal cells respectively. These observations strongly suggest that the intracellular pathway of vitellogenin secretion in chicken hepatocytes under the experimental conditions studied involves external stimuli and secretory vacuoles. The labelling of lysosomes may reflect catabolic turnover (crinophagy).