CONTROL OF SECRETORY LIPID DROPLETS IN THE HARDERIAN-GLAND BY TESTOSTERONE AND THE PHOTOPERIOD - COMPARISON OF 2 SPECIES OF HAMSTERS

Harderian glands of mammals secrete lipid. They are markedly sexually dimorphic in Syrian (golden) hamsters (Mesocricetus auratus): female g lands consist almost entirely of one cell type (type I) with small lip id droplets, whereas glands of males have both type I and type II cell s, with large lipid droplets. Siberian (Djungarian) hamsters (Phodapus sungorus) have sexually monomorphic Harderian glands, with both type I and type II cells. We used a morphometric technique to quantify the proportions of small (type 1) and large (type 2) lipid droplets in the se two species, in relation to the presence or absence of testosterone and to variations in the photoperiod. In Syrian hamsters, orchidectom y led to a marked increase in the proportion of type 1 lipid droplets in males kept in long (but not short)-day photoperiods. In contrast, t reatment of females with testosterone led to an increase in type 2 lip id droplets. Short-day photoperiods in both sexes led to an increase i n the proportion of type 2 lipid droplets and this was prevented by pi nealectomy. In Siberian hamsters, on the other hand, castration or sho rt photoperiods had no effect on Harderian gland morphology in either sex. These results suggest that some property of type 2 lipid droplets is important to Syrian hamsters during the autumn and winter. Syrian hamsters have a dimorphic Harderian gland and testosterone maintains t he basic sexual dimorphism during the long days of spring and summer; a pineal-mediated mechanism, perhaps the drop in serum prolactin level s, lends to an increase in type 2 lipid droplets with the short days o f autumn and winter. Siberian hamsters maintain levels of type 2 lipid droplets in both sexes and under all conditions of photoperiod, perha ps because of the colder conditions prevalent at all seasons of the ye ar in their native Siberian habitat. (C) 1995 Academic Press, lnc.