Prevention by pinealectomy of short‐photoperiod‐induced ultrastructural changes in the hamster harderian gland

Abstract

Harderian gland ultrastructure was examined at biweeky intervals for 16 weeks after either pinealectomy or sham‐operation of male and female hamsters kept in 1L:23D and 14L:10D photoperiods. Female characteristics such as membrane formations and extensive smooth endoplasmic reticulum appeared in the males kept under short photoperiod conditions. Similarly, male characteristics such as the tubular clusters appeared in the glands of females kept in the short photoperiod. When male and female hamsters were pinealectomized and exposed to the short photoperiod, the glands in each sex retained the characteristics typical of that sex. Atrophy of the testes and uteri was also observed in the sham‐operated hamsters maintained under short photoperiods, but not in the pinealectomized animals. The changes observed in the Harderian glands and reproductive organs of hamsters kept in the short photoperiod were not observed in the hamsters maintained in the long photoperiod. The photoperiod‐induced ultrastructural changes in the hamster Harderian glands are most likely due to changes in hormonal levels brought about by the regression of reproductive organs and can be prevented by pinealectomy.