Effects of monosodium-L-glutamate administration on serum levels of reproductive hormones and cholesterol, epididymal sperm reserves and testicular histomorphology of male albino rats

Abstract

This study investigated the effects of administration of monosodium Lglutamate (MSG) on serum gonadotrophin-releasing hormone (GnRH), luteinising hormone (LH), testosterone and total cholesterol (TC), cauda epididymal sperm reserves (CESR) and testicular histomorphology of adult male albino rats. Eighty-four rats, randomly assigned to 7 groups of 12 rats each, were used for the study. Varying low doses (0.25, 0.50 or 1.00 g/kg body weight) of MSG were administered orally or subcutaneously at 48-h intervals for six weeks. Serum GnRH, LH, testosterone and TC, and CESR were evaluated on days 14, 28 and 42 of MSG administration. Testicular histomorphology was evaluated on day 42. The results showed that the mean serum GnRH, LH and testosterone levels, and the CESR of all the treated groups were significantly (P < 0.05) lower than those of the untreated control on days 14, 28 and 42 of MSG administration. The mean serum TC levels of all the treated groups were also significantly (P < 0.05) lower than those of the control group on days 14 and 28. No lesions were observed on sections of the testes. It was concluded that MSG administration for 14, 28 and 42 days led to significantly lower serum levels of GnRH, LH, testosterone and TC, and significantly lower CESR.

The effects of monosodium l-glutamate administration on the reproduction and serum biochemistry of adult male rabbits

“…The absence of any obvious testicular histological lesions in all the groups in this study is in agreement with the reports of Igwebuike et al (2011) and Ochiogu et al (2015a) in rats, and Ochiogu et al (2015b) in goats. They used doses similar to the ones used in this study and they opined that MSG treatment may have impacted on testosterone production through its disruption of the hypothalamic-pituitary-testis regulatory axis, and not through any direct effect on testicular structure.…”

“…The significant lowering of the serum total cholesterol by MSG administration on Day 28 in this present study is corroborated by the reports of Bazzano et al (1970), Ochiogu et al (2015a) and Ochiogu et al (2015b) on studies with gerbils, rats and goats, respectively. However, it is not clear what effect this lowering of serum cholesterol exerted on testosterone concentrations in this study, as it is known that cholesterol is a precursor for testosterone biosynthesis (Hinshelwood 1998).…”

“…This is at variance with the reports of Tafelski and Lamperti (1977) and Ochiogu et al (2015a) who recorded immediate and earlier effects, respectively. Blaylock (1994) reported that different individuals have different tolerance thresholds to MSG.…”

“…It is therefore conceivable that in rabbits this threshold was overcome only by a relatively high dose and long duration of MSG administration and that subsequently the effects became evident. This lowering effect on the LH concentration could be attributed to the reported lesions MSG produces in the arcuate nucleus of the hypothalamus which secretes gonadotrophin-releasing hormone (GnRH) (Tafelski and Lamperti 1997;Ochiogu et al 2015a). The GnRH controls the biosynthesis and secretion of LH by the anterior pituitary (Norris 1997;Ochiogu et al 2015a;Ochiogu et al 2015b).…”

“…It is manufactured and marketed as a flavouring agent under various trade names such as Ac'cent ® , Aji-No-Moto ® , Vestin ® , Vedan ® and A-one ® . There are anecdotal reports that MSG is used to 'knock out' libido in male goats (Igwebuike et al 2011;Ochiogu et al 2014;Ochiogu et al 2015a; doi: 10.17221/8765-VETMED Ochiogu et al 2015b). Olney (1993) also reported the use of MSG as a bleaching agent in Nigeria.…”