Scholarly article on topic 'Monosodium glutamate induced testicular lesions in rats (histological study)'

Monosodium glutamate induced testicular lesions in rats (histological study) Academic research paper on "Biological sciences"

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{"Monosodium glutamate" / "Male rats" / Testis / Histopathology}

Abstract of research paper on Biological sciences, author of scientific article — Aisha D. Alalwani

Abstract Objective Monosodium glutamate (MSG) commonly consumed as a flavor enhancer and food additive in most soup, salad, and processed meat. The present study was designed to investigate the effect of MSG on testes of young male Wistar rats (n =30). Materials and methods They were randomly assigned into One control group C (n =10) received distilled water and two treatment groups A and B (n =10) were given oral daily doses of MSG 30 and 60g/kg body weight respectively for 2 months. Results The body weight of rats was significantly increased and mainly histological alterations which included of hyaline material in the lumina of the seminiferous tubules and interstitial tissues and exfoliation of spermatocytes and spermatids in treated group. Many cells of the different types of spermatogenesis appeared necrotic with pyknotic nuclei. Dilated congested blood vessels and vacuolar degeneration were also been observed in the cells of seminiferous tubules in the treated group B. Conclusions MSG may have some deleterious effects on the testes of Wistar rats and by extension may contribute to the causes of male infertility. Thus, it is important to reconsider the usage of MSG as a flavor enhancer.

Academic research paper on topic "Monosodium glutamate induced testicular lesions in rats (histological study)"

Middle East Fertility Society Journal (2013) xxx, xxx-xxx

Middle East Fertility Society Middle East Fertility Society Journal


Monosodium glutamate induced testicular lesions in rats (histological study)

Aisha D. Alalwani

Biology Department, Science Faculty for Girls, King Abdulaziz University, Jeddah, Saudi Arabia

Received 9 May 2013; accepted 26 September 2013


Monosodium glutamate;

Male rats;



Abstract Objective: Monosodium glutamate (MSG) commonly consumed as a flavor enhancer and food additive in most soup, salad, and processed meat. The present study was designed to investigate the effect of MSG on testes of young male Wistar rats (n = 30).

Materials and methods: They were randomly assigned into One control group C (n = 10) received distilled water and two treatment groups A and B (n = 10) were given oral daily doses of MSG 30 and 60 g/kg body weight respectively for 2 months.

Results: The body weight of rats was significantly increased and mainly histological alterations which included of hyaline material in the lumina of the seminiferous tubules and interstitial tissues and exfoliation of spermatocytes and spermatids in treated group. Many cells of the different types of spermatogenesis appeared necrotic with pyknotic nuclei. Dilated congested blood vessels and vacuolar degeneration were also been observed in the cells of seminiferous tubules in the treated group B.

Conclusions: MSG may have some deleterious effects on the testes of Wistar rats and by extension may contribute to the causes of male infertility. Thus, it is important to reconsider the usage of MSG as a flavor enhancer.

© 2013 Production and hosting by Elsevier B.V. on behalf of Middle East Fertility Society.

1. Introduction

Monosodium glutamate (MSG) known as AJI-NOMOTO is the sodium salt of glutamic acid (1). MSG contains 78% of glutamic acid, 22% of sodium and water (2). Glutamate is

one of the most common amino acids found in nature and is the main component of many proteins and peptides of most tissues. Glutamate is also produced in the body and plays an essential role in human metabolism. It is a major component of many protein-rich food products either in free or bound state of animals such as meat, fish, milk and cheese or vegetable origins such as mushroom and tomato (3). MSG is a widely used flavor enhancing food additive that may be present in packaged foods without appearing on the label. This flavor enhancer, not very long ago, was isolated in the laboratory, and identified as MSG. Modern commercial MSG is produced by fermentation of starch, sugar, beet sugarcane or molasses (4). This is particularly disturbing given the reported cases of

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MSG-induced adverse effects in animals (5), even at a relatively lower concentration (6).

Some reports indicated that MSG was toxic to human and experimental animals (7). MSG could produce symptoms such as numbness, weakness, flushing, sweating, dizziness and headaches. In addition, ingestion of MSG has been alleged to cause or exacerbate numerous conditions, including asthma, urticaria, atopic dermatitis, ventricular arrhythmia, neuropathy and abdominal discomfort (8). MSG has a toxic effect on the testis by causing a significant oligozoospermia and increases abnormal sperm morphology in a dose-dependent fashion in male Wistar rats (9). It has been implicated in male infertility by causing testicular hemorrhage, degeneration and alteration of sperm cell population and morphology (10). Previous scientific investigations aimed at determining the effect of MSG on testes (11,12). MSG caused a reduction in the sperm count (13).

In the last few years, fear had increased due to the adverse reactions and toxicity of MSG, with few and limited literature regarding the histological studies of the damage in testis treatment of animals with MSG. So the present study was designed to investigate the effects of monosodium glutamate on the tes-ticular tissue of young male rats.

2. Materials and methods

2.1. Chemical

The chemical used was monosodium glutamate (C5H9NO4.-Na) Purity 99% NT, it was sold in most open market in Jed-dah of Saud Arabia under the license of Ajinomoto co.INC. Tokyo, Japan. A stock solution was prepared by dissolving 30 and 60 g of MSG crystals in 100 ml of distilled water. The dose schedule was so adjusted that the amount of MSG administration per animal was as per their respective weight. The applied doses were selected according to (14).

2.2. Animals

This study was performed on 30 young male Wistar rats, weighing about 75-85 g b.wt. Animals were obtained from the animal house of the King Fahad Center for Medical Research, King Abdulaziz University in Jeddah. They were breeding in a well ventilated room with the temperature ranging between 22 and 25 0C and maintained under standardized conditions away from any stressful conditions with 12/12 light and dark cycle with free access to humidity and were fed dry balanced meal for experimental animals provided by the General Organization for Grain Silos and Flour Mills in Jeddah, with a constant source of water. All experimental procedures and animal maintenance were conducted in accordance with the accepted standards of animal care per cage (15-17).

2.3. Experimental design

The animals were divided randomly into three groups; each group included 10 rats. Group C (Control group): which received daily a single intraperitoneal (i.p.) injection of d.w. Group A: received daily a single dose of 30 mg/kg i.p. injection of MSG. Group B: received daily a single dose of 60 mg/kg i.p. injection of MSG. Rats were dissected 24 h after the end of

experimental period of 2 months. Body weight of each animal was determined at the beginning of the treatments and before being sacrificed. Testis of each animal was dissected out and weighed.

2.4. Morphological and behavioral changes

The behavioral and morphological changes that have taken place were recorded, and the body weight of the rats was recorded weekly at the beginning and end of the experimental periods.

2.5. Histological procedures of testis

At the end of the experimental period, the animals were sacrificed by cervical dislocation and the abdominal cavity was opened up to expose the testis which were quickly dissected out, weighed and fixed in 10% formal saline for routine histo-logical techniques. The tissues were dehydrated in an ascending grade of alcohol (ethanol), cleared in xylene and embedded in paraffin wax. Serial sections of 3-4 im thick were obtained using a rotator microtome. The deparaffinized sections were stained routinely with hematoxylin and eosin and mounted with DPX. Sections of testes were examined by light microscope. Photomicrographs of the desired sections were obtained for further observations. (18,19).

2.6. Statistical analysis

Data of body weights and testes of control and treated animals were analyzed statistically to assess the significant differences by using the Student's t-test for comparing the level of significance in the results between the MSG treated group and the untreated control.

3. Results

3.1. Behavioral and morphological observations

Severe diarrhea frequent urination with a repulsive smell, hemorrhage in the testis during anatomy, increased appetite and weak limb movement were observed in the rat group treated with MSG when comparing to control rats.

3.2. Body and testes weights

Comparison of the final body weights with the initial body weights in each group revealed a significant difference and hence the increase in groups A and B, respectively compared to the control group as well as increased relative testis weights in treated animal groups (Table 1).

3.3. Histological results

All rats in the control Group (C) showed normal histological pattern (Fig. 1a-c), whereas rats in groups administrated with MSG showed several tissue alterations of the seminiferous tubules. Sections of testes of rats in Group (A) that were given 30 mg/kg dose of MSG depicted severely slight to moderate damaged seminiferous tubules (Fig. 1d-f) as hyaline material

Table 1 Body weight and testis relative weight of experimental control rats and rats treated with MSG.

Animals groups Body weights 2 months 0 day Relative testes weight

Control (C) Mean ± S.D. P Mean ± S.D. P Mean ± S.D. P 206.301 ± 0.504 32.500 ± 0.408 1.007 ± 0.009

Treated (A) Treated (B) 229.500 ± 0.402 0.183 291.170 ± 1.462 0.008b 32.310 ± 0.707 1 32.280 ± 0.417 1 1.050 ± 0.052 0.013a 1.376 ± 0.024 0.007b

a P < 0.05. b P < 0.001.

Figure. 1 (a-f) Cross sections of testicular tissues of male Wistar rats; H&E. (a-c): testis sections of control rats (C):(a) Showing the normal histological structure of the seminiferous tubules (ST) populated by spermatocytes and late spermatids surrounded the tubular lumen, x400. (b) High power from previous figure (a) showing spermatogonia (SG), primary spermatocytes (PS), spermatids (SD), tubular basal lamina with sertoli cells (SC). Note myoid cell and narrow intertubular space contain interstitial leydig's cells (LC), x1000. (c) Showing epididymidis lumen full with the normal spermatozoa (S), x1000. (d-f) Sections of males' treated testes with 30 ml/kg MSG (A):(d) Showing deformed and atrophied seminiferous tubules (ST) populated by necrotic spermatocytes and spermatids with residual bodies in tubular lumen (arrows), whereas appeared vaculation (V) and sloughed germ cells from the basement membrane to the lumen of tubules (headarrows) with edematous (O) and congestion of interstitial tissues with leydg's cell necrosis, x400. (e) High power from previous figure (d) showing necrotic of spermatogonia and sertoli cells (arrows), vaculation (V) of spermatocytes in somniferous tubules with pyknotic nuclei (PY), x1000. (f): showing immature necrotic cells, deformed spermatozoa and residual bodies (arrows) in tubular lumen of epididymidis (arrows), x1000.

involved and widening of the spaces between seminiferous tubules (Fig. 1d). Some seminiferous tubules manifested grade damage that included disorganization of spermatogenesis cells. In addition where to edematous with congestion of interstitial tissues with leydig cells damaged (Fig. 1d and e). Damaged germ cells which separated from the basal lamina included vacuoles that were found inside the cytoplasm of spermatogonia and there was a loss of late spermatids. Sloughing and exfoliation of spermatocytes, spermatids and immature germ cells appeared into the lumen of the seminiferous tubules (Fig. 1f).

While 60 mg/kg dose of MSG of treated animals in Group (B) revealed a degenerative alteration which caused severe damage of germ cells and masses of necrotic cells were present in many tubules (Fig. 2a-f). Other tubules displayed marked elongated forms with hyaline material involving interstitial connective tissues, accompanied with leydig cells necrosis and lysis (Fig. 2a and b). Dilated congested inter tubular blood vessels were recorded in treated animals (Fig. 2c and d). Many cells in different types of spermatogenesis appeared vacuolar

degeneration with pyknotic nuclei which acquired deeply basophilic stain ability (Fig. 2b-d). Also destruction of most spermatogenesis' layers with the absence of spermatozoa was clearly recognized in other seminiferous tubules, maturation arrest in early and late stages of spermatids and numerous vacuoles of variable sizes in the seminiferous tubule spermatocytes and sertoli cells and interstitial connective tissues. Additionally, immature spermatids appeared in the lumina (Fig. 2e), epididymidis appeared full with deformed late spermatids, and loss of spermatozoa (Fig. 2f).

4. Discussion

Abnormal neurobehavioral changes recorded in the present work in animals treated with MSG, coincide with (20) who showed less limb movement. Whereas, effect on locomotion was observed by Alao et al. (21) in male and female rats. On the other hand, observations of the recent study indicated a

Figure 2 (2a-f): Cross sections of testicular tissues of male Wistar rats treated with 60 ml/kg MSG; H&E.(B)(a) showing disorganization of spermatogenic cells in seminiferous tubules, irregular basement membrane (headarrows). Note hyalinization (arrows) with loss of interstitial connective tissue cell and leydg's cells necrosis, x400. (b): High power from previous figures showing oedematous interstitum associated with cellular infilteration and eosinophilic droplates (arrows). with loss of interstitial connective tissue and leydg's cells, x1000. (c) Showing dilation and congested, vaculation (V) of spermatocytes and spermatogenic necrosis (arrows), x1000. (d): showing massive germ cells and spermatogonial necrosis and degeneration(arrows), damaged sertoli cell nuclei(headarrows). Note degenerated leydg's cells, x1000. (e) Showing immature spermatids and late spermatocytes (arrows), x1000. (f) Showing loss spermatozoa and deformed spermatids (arrows) and sloughing necrotic spermatocytes in tubular lumen (headarrows), x400.

significant increase in body and relative testis weight gain of MSG treated rat groups. Similar observations were also recorded by others in mice (20) in rats (22,23) and in female rats (24). MSG could improve the palatability of foods by exerting a positive influence on the appetite center, but it increases body weight (6). Although, MSG intake could induce an increase in energy intake (25) it could also lead to obesity (5) or alter the levels of carbohydrates, lipids and proteins in rats (26). However, (23,27) attributed the increased body weight to inflammation and edematous of tissue. The steady weight gain in groups treated with MSG possibly due to organ failure and shrinkage in subsequent toxicity by compounds was investigated by (28). A great deal of changes recorded in the current investigation are in accordance to the histological studies that were carried out on the testes of different animals treated with MSG, (11,29) found that the MSG induced histological changes in the testes of neonatal mice showed that both the germinal epithelium and Leydig cells were affected. Atallah (30) suggested that these histological changes may be due to either local effect of the chemical or indirectly caused by imbalance in gonadotrophic hormones. Balasubramanian et al. (31) explained the congestion of blood vessels as being due to the inhibition of prostaglandins synthesis, since these compounds are known to be involved in the regulation of testicular blood flow. Focusing on exfoliated, sloughing early spermatids and vacuolar degeneration in some damaged seminiferous tubule cells proved the presence of signs of deterioration. These cells of tubules (32) stated that vacuolation and exfoliation might be a sign of testicular toxicity and cell degeneration. Current work revealed pyknosis of cell nuclei may indicate the loss of functional efficiency of the cells. Similar results have been demonstrated by (33) on male rats treated with MSG.

The maturation arrest observed in the present study was explained by (34,35) who correlated this arrest to the testosterone inhibition which caused stopping of spermatogenesis. Previous researches have explained the mechanisms by which MSG inhibited the spermatogenesis in the current experiment. Glutamate receptors are present in different tissues: the hypothalamus, spleen, thymus, liver, kidneys, endocrine system, ovaries, etc. (36,37). Earlier studies proved the presence of functional glutamate transporters and receptors in testes of rats (37,38) and (39) in mice. Therefore, testes are considered as a target organ for MSG. So, one of the mechanisms may be a direct effect of MSG via glutamate receptors and transporters on the epithelial cells of the seminiferous tubules. The second mechanism was proved by other researchers (40,41) who stipulate that there are neurotoxin effects of MSG on the function of hypothalamus-pituitary-gonadal system. The effects of such toxicants on male reproduction may be anatomical or only functional, depending on whether they produce structural changes in the reproductive system, or merely affect the functions of the reproductive organs (42). Franc et al. (43) reported that the central nervous system of MSG-treated animals showed neurogenic function in the levels of FSH, LH and testosterone. These hormones are essential for normal testis function and healthy spermato-genesis. In mammals, spermatogenesis is totally dependent upon testosterone (44,45). Glutamate is a predominant excitatory neurotransmitter in the mammalian central nervous system (46-48). Such excessive activation of glutamate receptors and overloading with intracellular calcium can induce neural death (49). Therefore, the present study suggested that

spermatogenesis was affected indirectly via the hypothalamic lesions. The ability of monosodium glutamate to damage nerve cells of the hypothalamus is a pointer to the fact that it may alter the neural control of reproductive hormone secretion via the hypothalamic-pituitary-gonadal regulatory axis. Such alterations in reproductive hormone secretion may adversely affect the reproductive capacity of the affected animals. The third mechanism reported that exposure to MSG resulted in a decrease in the testicular ascorbic acid level that could lead to oxidative damage in rat testes (13,50), and oxidative damage in different organs (51-53). There was a significant reduction in the caudal epididymal sperm reserves of the rats that received monosodium glutamate relative to the control rats. Present results agree with, previous studies that found that animals treated with MSG revealed a reduction in sperm count. (41,13,12) showed that the indication is that the reduced caudal epididymal sperm counts observed in the MSG-treatment rats may be the end result of a considerable decline in the influence of testosterone on spermatogenesis in these rats.

5. Conclusion

The results of the present investigation have shown that MSG at low and high doses are capable of producing alterations in the body weights and testis tissue of Wistar rats and by extension the MSG treatment may contribute to the causes that led to infertility problem in rats which along with its reactions and toxicity led to an increased fear in the last few years. Thus, it is important to reconsider the usage of MSG as a flavor enhancer.


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