Sequential changes in the harderian gland of rats exposed to high intensity light.

We examined sequential changes in histology, fluorescent microscopy, and porphyrin content in the Harderian glands of 55 male Wistar rats exposed to fluorescent light of 2,500 or 1,600 lux for 12 h a day up to 8 days and of 10 control rats. After exposure for 1 day there was severe necrosis of the glandular cells, with edema and cellular infiltration of the Harderian gland adjacent to the retina. After exposure for 4 and 8 days these changes regressed and glandular cells regenerated. Red fluorescence in frozen sections of glands from control rats was interpreted to be due to porphyrins. The red fluorescence was faint in glandular acini injured by exposure to light for 4 and 8 days, and porphyrin content of the gland decreased after 4 and 8 days. Homogenates of the Harderian glands from five control rats caused marked hemolysis after exposure to sunlight. Thus exposure to high-intensity light induced necrosis of the glandular cells in the Harderian glands. The injury appeared to be a direct effect of light on the glandular cells, probably as a result of photodynamic action on the porphyrins in the gland.(ABSTRACT TRUNCATED)