Abstract
The present study was undertaken to clarify the strain differences between ICR and BALB/c mice and sex differences in ICR mice in the sequential changes by the photic damage to the Harderian gland and the correlation between Harderian gland damage and porphyrin content. The animals were exposed to fluorescent light at 3, 000 lux for 12 hr a day for 2, 4 or 8 days. On day 2, the Harderian glands showed marked necrosis and luminal dilation with secretion and inflammatory edema. Photic damage was observed in a restricted area just behind the eye in both strains. ICR mice showed extensive and diffuse necrosis of the glandularcells, but BALB/c mice showed sparsely scattered necrosis of glandular cells, that is, the extent of damage was more marked in ICR mice than in BALB/c mice. With prolongation of exposure period the glandular necrosis was improved and cell regeneration was accompanied by squamous metaplasia. The red fluorescence of the glands under ultraviolet light was intense in ICR mice and faint in BALB/c mice correlating with the porphyrin contents in Harderian glands. The fluorescence faded completely in the damaged acini and the intraluminal porphyrin accretions were also significantly decreased after light exposure. The photohemolytic activity of the Harderian gland homogenate was much stronger in ICR mice than in BALB/cmice. There was no obvious sex difference in any of these variables in ICR mice.In conclusion, there was a marked strain difference between ICR and BALB/c mice in Harderian gland vulnerability to photic damage, and this difference highly correlated with the porphyrin contents in the Harderian glands. The photic damage to the Harderian glands may be due to photodynamic action of the porphyrins present in the glands.
