Pinealectomy and Melatonin Administration in Rats: Their Effects on Plasma Leptin Levels and Relationship with Zinc
The aim of this study was to examine effects of pinealectomy and melatonin administration plasma leptin levels and its relationship with zinc in rats. The study was conducted on 40 adult male Sprague-Dawley rats. They were divided into four groups each containing 10 animals. Group 1 served as control. Group 2 was pinealectomized group. Animals in Group 3 were pinealectomized and injected with melatonin (3 mg/kg/day, ip). Group 4 received melatonin alone (3 mg/kg/day, ip). At the end of the experiments, all animals were decapitated and trunk blood collected. Plasma leptin and zinc levels were determined by radioimmunoassay and Atomic Absorption Spectrophotometer methods, respectively. Although mean weights of the animals at the beginning were not significantly different among the groups, the mean weight of the pinealectomized group was found to be significantly lower than all other groups at the end of a six-month period (p < 0.01). Plasma leptin and zinc levels were the highest in mela-tonin-administered group (group 4; p < 0.01). The lowest plasma leptin and zinc levels were obtained in the pinealectomized group (group 2; p < 0.01). Changes in these two parameters were not statistically significant in groups 1 and 3. Our findings indicate that pinealectomy results in a decrease in leptin and zinc levels in rats, and that melatonin administration to pinealectomized rats prevents the decrease in the these parameters. In addition, long-term administration of melatonin to rats leads to an increase in both leptin and zinc concentrations.
KeywordsPinealectomy melatonin administration leptin zinc
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Supported in part by a Research Fund of Selcuk University Grant no: TF 2001/045. We would like to thank to Dr. Bayram Yilmaz of Firat University Medical School for his critical evaluation and English correction of the manuscript.
- 6.Bediz, C. S., Baltaci, A. K., Mogulkoc, R. (2003) Both zinc deficiency and supplementation affect plasma melatonin levels in rats. Acta. Physiol. Hung. 90, 353–359.Google Scholar
- 11.Chen, M. D., Song, Y. M., Lin, P. Y. (2000) Zinc may be a mediator of leptin production in humans. Life Sci. 66, 214–219.Google Scholar
- 12.Collins, S., Kuhn, C. M., Petro, A. E., Swick, A. G., Chrunyk, B. A., Surwit, R. S. (1996) Role of leptin in fat regulation. Nature 380, 677.Google Scholar
- 13.Considine, R. V., Sinha, M. K., Heiman, M. L., Kriauciunas, A., Stephens, T. W., Nyce, M. R., Ohannesian, J. P., Marco, C. C., McKee, L. J., Bauer, T. L., José, F., Caro, J. F. (1996) Serum immunoreactive-Leptin concentrations in normal-weight and obese humans. N. Engl. J. Med. 334, 292–295.PubMedGoogle Scholar
- 16.Gainsford, T., Wilson, T. A., Metcalf, D., Handman, E., McFarlane, C., Ng, A., Nicola, N. A., Alexander, W. S., Hilton, D. J. (1996) Leptin can induce proliferation, differentiation and functional activation of hemopoietic cells. Proc. Natl. Acad Sci. U.S.A. 93, 14564–14568.PubMedPubMedCentralGoogle Scholar
- 22.Mangian, H. F., Lee, R. G., Paul, G. L., Emmert, J. L., Shay, N. F. (1998) Zinc deficiency suppresses plasma leptin concentrations in rats. J. Nutr. Biochem. 9, 47–51.Google Scholar
- 23.Mantzoros, C. S., Flier, J. S., Rogol, A. D. (1997) A longitudinal assessment of hormonal and physical alterations during normal puberty in boys: rising leptin levels may signal the onset of puberty. J. Clin. Endocrinol. Metab. 82, 1065–1070.Google Scholar
- 30.Mocchegiani, E., Santarelli, L., Tibaldi, A., Muzzioli, M., Bulian, D., Cipriano, K., Olivieri, F., Fabris, N. (1998) Presence of links between zinc and melatonin during the circadian cycle in old mice: effects on thymic endocrine activity and on the survival. J. Neuroimmunol. 86, 111–122.PubMedGoogle Scholar
- 31.Mocchegiani, E., Perisin, L., Santarelli, L., Tibaldi, A., Zorzet, S., Rapozzi, V., Giacconi, R., Bulian, D., Giraldi, T. (1999) Melatonin administration in tumor-bearing mice (intact and pinealectomized) in relation to stress, zinc, thymulin and IL-2. Int. J. Immunopharmacol. 21, 27–46.PubMedGoogle Scholar
- 33.Mustonen, A. M., Nieminen, P., Hyvarinen, H., Asikainen, J. (2001) Exogenous melatonin elevates the plasma leptin and thyroxine concentrations of the mink (Mustela vison). Z. Naturforsch. [C] 55, 806–813.Google Scholar
- 35.Ott, E. S., Shay, N. F. (2001) Zinc deficiency reduces leptin gene expression and leptin secretion in rat adipocytes. Exp. Biol. Med. (Maywood) 226, 841–846.Google Scholar
- 46.Skwarlo-Sonta, K. (1996) Functional connections between the pineal gland and immune system. Acta Neurobiol. Exp. (Wars.) 56, 341–357.Google Scholar
- 50.Wilkinson, M., Arendt, J., Bradtke, J., de Ziegler, D. (1997) Determination of a dark-induced increase of pineal N-acetyl transferase activity and simultaneous radioimmunoassay of melatonin in pineal, serum and pituitary tissue of the male rat. J. Endocrinol. 72, 243–244.Google Scholar
- 51.Wolden-Hanson, T., Mitton, D. R., McCants, R. L., Yellon, S. M., Wilkinson, C. W., Matsumoto, A. M., Rasmussen, D. D. (2000) Daily melatonin administration to middle-aged male rats suppresses body weight, intraabdominal adiposity, and plasma leptin and insulin independent of food intake and total body fat. Endocrinology 141, 487–497.PubMedGoogle Scholar
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