Chronic administration of melatonin induces changes in porphyrins and in the histology of male and female hamster Harderian gland: Interrelation with the gonadal status

Abstract

In this paper, we have investigated the influence of melatonin on the histology and porphyrin content of the Syrian hamster Harderian glands. Daily afternoon injections of 25 micrograms of melatonin to female hamsters for 12 weeks resulted in the discontinuity of estrous cyclicity, a marked decrease in the Harderian gland intraluminal area occupied by porphyrins, and in a significant rise in the number of Type II cells. A similar decrease in porphyrins was observed after 8 weeks of ovariectomy. However, if the melatonin injections were given for only 8 weeks (without inducing gonadal atrophy), no changes were observed in the area occupied by intraluminal porphyrins, suggesting that the effects of melatonin in female Syrian hamsters might be associated with the subsequent gonadal atrophy. Castration of male hamsters induced a significant increase in porphyrins and a clear drop in the number of Type II cells. These changes were totally prevented when melatonin was administered daily from the day of castration. Our results suggest that melatonin, at least in male Syrian hamsters, plays a role in Harderian metabolism, acting directly on the Harderian secretory cells or indirectly through pituitary hormones.

Effects of the circadian mutation ‘tau’ on the Harderian glands of Syrian hamsters

“…In all previous studies, type II cells were low in HGs of untreated wild-type females and inversely correlated with porphyrin accumulation. Never had such a considerable percentage of type II cells been found in normal females [Rodrõ Âguez-Colunga et al, 1991Mene Ândez-Pela  ez et al, 1992]. Only treatments affecting gonadosteroids, leading to virilization, caused rises in type II cells, though in conjunction with decreases in porphyrins; therefore, induced interconversions between feminine and masculine phenotypes always maintained this inverse correlation [Payne et al, 1977;McMasters and Hoffmann, 1984;Payne, 1994].…”

Immunohistochemical evidence for the presence of tryptophan hydroxylase and serotonin in the rodent Harderian gland

“…This suggests that melatonin produced by type I cells probably acts on type II cells (paracrine effect of melatonin). Exogenous melatonin administration has been demonstrated to reduce the area occupied by intraluminal porphyrin accretions (Rodriguez-Colunga et al 1991) and the expression of the aminolevulinate synthase (the rate-limiting enzyme for porphyrin synthesis) gene and leads to decrease porphyrin concentrations (Dubey and Haldar 1997) in the rodent Harderian gland. Recently, Princ et al (1998) and Carneiro and Reiter (1998) have shown that, in the brain, melatonin prevents the damage induced by free radicals generated by porphyrin metabolism.…”

Regulation of the aminolevulinate synthase gene in the Syrian hamster Harderian gland: Changes during development and circadian rhythm and role of some hormones

“…Lighting conditions clearly influence the effects of androgens on porphyrin concentrations and HG morphology (Clabough and Norvell, 1973;Formgren and Wetterberg, 1976;Van Jaarsveld et al, 1989;Weterberg, 1972). Melatonin has been found to decrease porphyrin concentration and porphyrin deposits in the HG and serum levels of thyroid hormones in the female Syrian hamster (Hoffman et al, 1989~;Rodriguez-Colunga et al, 1991). Also, Menendez-Pelaez et al (1993) demonstrated the presence of melatonin binding sites in the HG of Syrian hamsters.…”