Endogenous avidin found in the magnum gland of the hen oviduct. Comparative cytochemical studies utilizing both biotinyl-peroxidase and immunoperoxidase methods.

The location of endogenous avidin was studied cytochemically in the magnum tissue of the oviduct of laying hens. Two methods, based on an interaction of avidin-biotin with biotin hydrazide-peroxidase (B-HRP) as an affinity reagent, and on an immunoperoxidase technique, were tested by morphological analysis. The data obtained by both methods showed that in the magnum B-HRP is a strictly substitutive reagent for endogenous avidin. Avidin was clearly demonstrated in large amounts in the secretory granules of some epithelial cells and tubular gland cells, but was absent from mucous cells, the goblet cells, which had been believed to be the location of avidin production, and from ciliated cells. These granules had previously been demonstrated by both electron-microscopic cytochemical techniques. Especially in acinar cells, they were nonhomogeneous with a speckled core and a dense peripheral part. They ranged in size from 500 to 2200 nm in diameter in the gland and 180 to 720 nm in the epithelium. Columnar epithelial cells containing avidin granules had a strong resemblance to those of the protodifferentiated tubular gland cells in the magnum of chicks pretreated with daily estrogen or estrogen plus progesterone, and might have migrated towards the acinus as substitutional secretory cells. Therefore, the acinar cells of the magnum, considered to be composed of several secretory protein-producing systems, are dependent on estrogen and/or progesterone in the oviduct of the laying hen.