Anat Cell Biol.  2019 Sep;52(3):286-295. 10.5115/acb.18.122.

Effect of melatonin on the onset of puberty in male juvenile rats

• Venugopal

• KMID: 2459544
• DOI: http://doi.org/10.5115/acb.18.122

Abstract

Melatonin or N-acetyl-5-methoxytryptamine, the fascinating molecule secreted by the pineal gland. Melatonin has a close interaction with hypothalamic-pituitary-gonadal axis. In non-seasonal breeders like rat its exact role in reproduction is controvertible. So it is worth to explore the possible role of melatonin on the onset of puberty in male albino rats. Two groups of male rats aged 5 and 10 days were used for the study. In each group, there were three subgroups, each receiving melatonin for 5 days, 10 days or till the day of descent of testes. Similar subgroups were used as controls. Without handling, animals were observed daily for the onset of puberty. On the day of descent of testes, body weight of the animal was noted, blood was collected, serum was separated and used for radio immunoassay. For histomorphometric analysis, all morphometric measurements were done using an occular micrometer. Volume fraction of seminiferous tubules, intertubular connective tissue of testes, cortex and medulla of thymus were estimated by point count method. In both the age groups melatonin advanced the age on descent of testes, increased the body weight, organ weight. It also increased the serum hormone levels. So, in conclusion this study indicates that exogenous melatonin advances the onset of puberty in male albino wistar rats and this effect is more pronounced in the younger animals.

Keyword

Descent of testes; Hormones; Melatonin; Onset of puberty

MeSH Terms

Adolescent
Animals
Body Weight
Connective Tissue
Humans
Immunoassay
Male*
Melatonin*
Methods
Organ Size
Pineal Gland
Puberty*
Rats*
Rats, Wistar
Reproduction
Seminiferous Tubules
Testis
Thymus Gland
Melatonin

Figure

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  Fig. 1 (A) Control rat testis (H&E stain, ×100) showing normal tubular diameter, less compactness of tubules and normal interstitial connective tissue. (B) Melatonin (MT) treated rat testis showing increased tubular diameter, more compactness of tubules and reduced interstitial connective tissue (H&E stain, ×100). (C) Control rat testis (H&E stain, ×500) showing normal tubular diameter, less compactness of tubules and normal interstitial connective tissue. (D) MT treated rat testis showing increased tubular diameter, more compactness of tubules and reduced interstitial connective tissue (H&E stain, ×500).

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  Fig. 2 (A) In situ thymus gland of control rats (H&E stain, ×125) showing normal central medulla and peripheral cortex. (B) In situ thymus gland of melatonin treated rats showing increased, dense, wider cortex and lesser medulla (H&E stain, ×125).

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  Fig. 3 (A) Effect of melatonin (MT) on luteinizing hormone (LH) in 5-day-old rats. MT treatment shows significant increase in LH levels compared to control. (B) Effect of MT on LH in 10-day-old rats. MT treatment shows significant increase in LH levels compared to control. *P<0.05, **P<0.01.

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  Fig. 4 (A) Effect of melatonin (MT) on testosterone in 5-day-old rats. MT treatment shows significant increase in testosterone levels compared to control. (B) Effect of MT on testosterone in 10-day-old rats. MT treatment shows significant increase in testosterone levels compared to control. *P<0.05, **P<0.01.

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  Fig. 5 (A) Effect of melatonin (MT) on growth hormone (GH) in 5-day-old rats. MT treatment shows significant increase in GH levels compared to control. (B) Effect of MT on GH in 10-day-old rats. MT treatment shows significant increase in GH levels compared to control. *P<0.05, **P<0.01.

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  Fig. 6 Schematic representation of action of melatonin on pancreas. IGF, insulin-like growth factor.

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  Fig. 7 Schematic representation of mechanism of action of melatonin on gross, histological and hormonal parameters. LH, luteinizing hormone; GH, growth hormone; IGF-1, insulin-like growth factor 1.

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