Pinealectomy Increases and
Exogenous Melatonin Decreases Leptin Production in Rat Anterior
Pituitary Cells:
an Immunohistochemical Study
I. KUS1, M. SARSILMAZ1, N. COLAKOGLU2,
A. KUKNER2, O. A. OZEN1, B. YILMAZ3,
H. KELESTIMUR3
Departments of Anatomy1, Histology and Embryology2
and Physiology3, Medical School,
Firat University, Elazig, Turkey
Received May 16, 2003
Accepted October 15, 2003
Summary
Melatonin, the main hormone of the pineal gland, informs the
body about the environmental light and darkness regimen, which
in turn contributes to the photoperiodic adaptation of several
physiological functions. Leptin, the hormone secreted mainly by
adipocytes and some other tissues including the pituitary,
informs the brain about the mass of adipose tissue, which plays
an important role in energy homeostasis. Melatonin has been
shown to decrease circulating leptin levels. It is currently not
known whether melatonin has an effect on leptin synthesis in the
pituitary. The aim of this study was to immunohistochemically
examine the effects of pinealectomy and administration of
melatonin on leptin production in the rat anterior pituitary.
The pituitary samples obtained from 18 male Wistar rats
including sham-pinealectomized, pinealectomized and
melatonin-injected pinealectomized groups were
immunohistochemically evaluated. Immunostaining of leptin was
moderate (3+) in sham-pinealectomized rats, heavy (5+) in
pinealectomized rats and low (1+) in melatonin-treated
pinealectomized rats, respectively. The present results indicate
that pinealectomy induces leptin secretion in anterior pituitary
cells, and this increase of leptin synthesis can be prevented by
administration of melatonin. Thus, melatonin seems to have both
physiological and pharmacological effects on leptin production
in the anterior pituitary of male rats.
Key words
Leptin • Melatonin • Pinealectomy • Anterior Pituitary • Rat
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