POSTNATAL-DEVELOPMENT OF CELL-TYPES IN THE HAMSTER HARDERIAN-GLAND

The morphology, frequency, and distribution of mitotic cells in the ep ithelium of the Harderian gland was studied in the male and female ham ster from birth to the ninetieth day of postnatal life using light and electron microscopic techniques. The results obtained show that there is a gradual decline in the mitotic activity of the Harderian gland a s the animals become older which continues until sexual maturity is re ached. The study did not find any morphological evidence for the exist ence of separate precursor cells for the different secretory cell type s of the gland. Secretory cells seem to be a homogeneous population in the glands of hamsters younger than 20 days. Cells that could be inte rpreted as undifferentiated stem cells were not observed. Mitotic cell s were observed randomly distributed within tubulo-alveoli, similar to those in interphase. The first sex differences were observed at day 2 0, when type II cells appeared in male glands. From this point, the pe rcentage of type II cells rapidly increased in male glands. This incre ase was not accompanied by an increase in the global mitotic activity. However, at this age, male type II cells develop an intense mitotic a ctivity. The observations obtained are in accordance with the hypothes is that the type I and type II cells have the same cell precursor. (C) 1996 Wiley-Liss, Inc.