Alloxan-Induced Diabetes and the Pineal Gland: Differential Effects on the Levels of Pineal N-Acetylserotonin, Pineal Melatonin, and Serum Melatonin

Authors

  • S. F. Pang,

    Corresponding author
    1. Department of Physiology, Faculty of Medicine, University of Hong Kong (S. F. P., F. T.), and Department of Applied Sciences, Hong Kong Polytechnic (P. L. T.)
      Address reprint requests to Dr. S. F. Pang, Department of Physiology, University of Hong Kong, Sassoon Road, Hong Kong.
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  • F. Tang,

    1. Department of Physiology, Faculty of Medicine, University of Hong Kong (S. F. P., F. T.), and Department of Applied Sciences, Hong Kong Polytechnic (P. L. T.)
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  • P. L. Tang

    1. Department of Physiology, Faculty of Medicine, University of Hong Kong (S. F. P., F. T.), and Department of Applied Sciences, Hong Kong Polytechnic (P. L. T.)
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Address reprint requests to Dr. S. F. Pang, Department of Physiology, University of Hong Kong, Sassoon Road, Hong Kong.

Abstract

Effects of alloxan treatment on the levels of pineal melatonin, pineal N-acetylserotonin, and serum melatonin were investigated. Male rats were housed under a photoperiod of 12 h light: 12 h darkness and a temperature of 23 ± 3°C. Three weeks after alloxan (170 mg/kg) or carrier injection (s. c.), the animals were killed at mid-light (1200 h) and mid-dark (2400 h). Pineal and serum indoles were extracted and quantified by radioimmunoassays. It was found that pineal levels of N-acetylserotonin in the diabetic rats were significantly higher (P < 0.05) than those of the controls. Conversely, pineal and serum levels of melatonin in the control rats were significantly higher (P < 0.05) than those of the alloxan-induced diabetics. Our results suggest that alloxan-induced diabetics may decrease pineal melatonin synthesis in rats by reducing the activity of hydroxyindole-O-methyltransferase, resulting in a decrease in pineal melatonin secretion.

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