NEW INSIGHTS INTO THE CYTODYNAMICS OF THE HAMSTER HARDERIAN-GLAND AS PROVIDED BY THE BROMODEOXYURIDINE-LABELING METHOD

The fourth week of postnatal life is a critical point in the developme nt of the hamster Harderian gland. During this week, cells with large lipid vacuoles (type-II cells) appear in the male gland, marking a mor phological sex difference that is notorius in adult animals. The origi n and fate of type-II cells are controversial. To gain insight into th e mechanisms by which type-II cells become a major cell type in the gl and of adult male hamsters, bromodeoxyuridine (BrdU) labelling was use d to assess the proliferative activity of both types of glandular cell s in 28-day-old animals, To search for possible sex differences in the proliferative activity of this gland, female animals of the same age as the males were also studied. No difference was found in the overall labelling index (BrdU-labelled cells/100 cells) between males (1.8+/- 0.1%) and females (1.5+/-0.1%). In the gland of the males, the specifi c labelling index of type-II cells (3.4+/-0.4%) was significantly high er than that of type-I cells (0.9+/-0.2%). Interestingly, the proporti on of type-II cells present in the male glands at this age (36.6%) was significantly lower than that of type-I cells. Our results strongly s uggest that the proliferation of type-II cells, rather than a continuo us differentiation of these cells from preexisting type-I cells, is a major event in the achievement of the mature form of this gland. The r esults reported here counsel a reappraisal of current theories about t he cytodynamics of the hamster Harderian gland.