Unusual Peroxidase-positive Granules in the Developing Rat Submaxillary Gland

Unusual peroxidase-positive granules exist in a particular cell type in the rat submaxillary gland during the first 2 wk after birth . The granules display remarkable substructure and clearly show cytochemical evidence of endogenous peroxidase activity . The cells containing the peroxidase-positive granules comprise portions of the terminal end pieces, or so-called "terminal tubules" (4), in the developing submaxillary gland. (The terminal tubules are transient structures that eventually will give rise to mature acini [4]) . Along with the cells containing the peroxidasepositive granules, another cell type also exists in the terminal tubules at birth . It contains homogeneous granules which do not stain for peroxidase . It is not until about the fifth day after birth that a third, acinar type cell, is seen . The purpose of this preliminary report is to focus upon a description of the unusual peroxidase-positive granules as they are seen at different stages of submaxillary gland development .