X-ray irradiation of orbital glands of the rabbit.

Abstract

The rabbit and most vertebrates have two orbital glands opening onto the conjunctiva or conjunctival appendages (1, 2). One, a sebaceous gland, called the harderian gland, which is connected with the nictitating membrane, has only a vestigial counterpart in man. The other is a true lacrimal gland opening onto the conjunctiva and is functionally and histologically similar to the lacrimal gland of man. Together these glands form a substantial part of the orbital contents. The effect of ionizing radiations on the lacrimal gland is of some importance because of its possible role in the keratoconjunctivitis (3, 4) following irradiation and because of the occasional therapeutic irradiation of the lacrimal gland for epiphora (5–10). It seemed desirable, therefore, to put on record the present data, collected as part of a more comprehensive study of radiation effects on the eye, indicating the changes or lack of changes which occur in the orbital glands from amounts of ionizing radiations that are likely to be encountered in radiotherapy. Experimental studies on irradiation of the orbital glands of the rabbit have been few (7). No gross or histologic changes have been characteristically found, but since the studies were done prior to the development of roentgen dosimetry, the amount of radiation which the glands received is open to question. In the experiments to be reported here the right eyes of approximately 100 rabbits were irradiated with various doses from a 1.2-mev x-ray machine,2 ranging from 75 to 4,000 r. The animals were killed at different times after irradiation, the eyes were removed, and the orbital glands dissected out from the irradiated and non-irradiated sides. The glands were then weighed and embedded in paraffin for routine sectioning. Anatomic Considerations The harderian gland is a white lobulated gland, weighing approximately 1.5 gm. in the adult rabbit. Situated in the anterior or nasal part of the orbit, it is attached to the base of the nictitating membrane and extends back into the orbit about 1.5 cm. It is in contact with much of the anterior and inferior portion of the globe. Histologically the harderian gland consists of acini having lumina up to 0.5 mm. in diameter (Fig. 1). These acini are lined by a single layer of cuboidal cells that are seen with the Sudan stain to be filled with fat but which with hematoxylin and eosin reveal a delicately reticulated cytoplasm and a round or ellipsoid nucleus situated usually in the approximate center of the cell. Although the cells are uniform for any one lobule, there is some variation in different lobules. In some portions of the gland the cytoplasm is more compact and the nuclei may be situated at the base of the cells. Within the lumina of the acini there is often a reticulated substance (secretion?) identical with that of the cell.