Experimental modification of vitellogenesis in Japanese quail by trypan blue in vivo.

Ovaries of adult Japanese quails were exposed in vivo to the acid bisazo dye trypan blue (TB) which binds to plasma albumin, the plasma precursor of the yolk protein alpha-livetin. By a combination of fluorescence microscopy and electron microscopy alpha-livetin could be localized in the subdroplets of intermediary and yellow yolk spheres. Trypan blue alters vitellogenesis in the non-disc region of follicles in rapid growth in a reversible and dose-dependent way. Less yolk is produced over 24 h and its morphology is different when compared to controls. This yolk is similar to yolk of the germinal disc region where vitellogenesis is known to be inhibited physiologically. Several ultrastructural features of the germinal disc region are also found in the non-disc region of TB-exposed follicles. Our results suggest that the morphology of yellow yolk is linked to the rate of deposition. We propose that the inhibitory action of TB on vitellogenesis can be explained by a defective receptor-ligand dissociation in endosomes.