POSTNATAL-DEVELOPMENT OF THE HARDERIAN-GLAND IN THE RABBIT - LIGHT AND ELECTRON-MICROSCOPIC OBSERVATIONS

We have investigated the development of the Harderian glands of Japane se white rabbits from birth to 4 months of age. Although two types of secretory cells comprise the glandular epithelium of the pink and whit e lobes in fully developed glands, the time of neonatal appearance is different between the two. Cells consisting of the pink lobe first app ear on the third day of life, while cells of the white appear around s eventh day of life. The ultrastructure of the Harderian glands from 1- week-old rabbits resembles that of adult animals. The gland can be div ided into three parts on the basis of their epithelial cell, compositi on at the electron microscopic level. The respective parts are compose d of: (1) one type of cells with large vacuoles (pink lobe), (2) one t ype of cells with small vacuoles (white lobe), and (3) two types of ce lls with large and small vacuoles (pink-white mixed portion), The rela tive number of plasma cells per 1 mm(2) is low in both pink and white lobes during early postnatal Life, However, in adult animals, the whit e lobe has a larger number of plasma cells than the pink lobe. These r esults suggest the possibility that the white lobe participates in the immune system more than does the pink. (C) 1997 Wiley-Liss, Inc.