Effects of brefeldin A on the synthesis and secretion of egg white proteins in primary cultured oviduct cells of laying Japanese quail (Coturnix coturnix japonica).

We investigated the effect of brefeldin A (BFA) and monensin on the secretion of egg white proteins in primary cultured oviduct cells. Monensin inhibited the secretion of egg white proteins, but this drug also caused morphological changes of the cells and inhibited their protein synthesis. BFA inhibited protein secretion without any remarkable morphological changes of the cells and without significant inhibition of protein synthesis. In the presence of BFA at 1 microgram/ml, only 10% of synthesized ovalbumin was secreted into the medium even after 6 h. A similar effect of BFA was shown in the case of conalbumin. When the cells were cultured in the presence of BFA, precursors of mature ovalbumin accumulated which were not secreted. Their affinity for lectin binding affinity columns (Con-A Sepharose and WGA-agarose) suggested that they contained immature high-mannose-type chains. The above results suggest that the conversion of high-mannose-type oligosaccharides to hybrid-type ones, which is not usually observed in mammalian species but only in avian oviduct tissues, proceeds between the Golgi complex and the endoplasmic reticulum.