IMMUNOCYTOCHEMICAL LOCALIZATION OF MELATONIN IN THE HARDERIAN-GLAND OF SYRIAN-HAMSTER

Background: The Harderian gland (HG) is a tubulo-alveolar gland found within the ocular orbit of animals which present a nictitating membran e. The Harderian gland is regarded as an extrapineal melatonin produci ng organ and both, photoperiod and melatonin have been shown to exert an important role in the metabolism and morphological features of such a gland. Our results seem to support the presence of melatonin in the nuclei of the HG cells, although our studies have not definitively pr oved such presence. Methods: An Immunocytochemical anti-melatonin tech nique was done over free sections of Bouin fixed material obtained fro m Syrian hamsters. Some of the sections were embedded in an epoxy resi n and studied under electron microscope. Results: The presence of posi tive immunoreaction was observed at the level of the nuclear membranes and in close relation to chromatin. No differences were observed betw een males and females nor between pinealectomized animals and control ones. Conclusions: Our results suggest the binding of melatonin to the cell nucleus in an cell types of the gland. These observations are in accord with the binding studies performed by Acuna-Castroviejo in pur ified cell nuclei of rat liver (Acuna-Castroviejo et al., 1994. J. Pin eal Res., 16:100-112) and the earlier one by Menendez-Pelaez et al. (1 993a,b, J. Pineal Res., 15:59-69; J. Cell Biochem., 53:373-382) using the Light microscope. Our results seem to support the idea of a nuclea r action of melatonin and they agree with the observations of Carlberg and Wiesenberg (1995, J. Pineal Res., 18:171-178) about the activatio n of some orphan receptors by melatonin. (C) 1996 Wiley-Liss, Inc.