Infiltration of Inflammatory Cells in the Ovary Following Oral Administration of Monosodium Glutamate

Background: Monosodium glutamate (MSG) a sodium salt of naturally occurring (non-essential) L-form of glutamic acid is one of the main flavor enhancer used as an ingredient in various food products. It is widely used in restaurants, packaged food industries and household kitchens, in Nigeria, most communities and individuals often use MSG as a bleaching agent for the removal of stains from clothes. Materials and Methods: Twenty (20) female adult wistar rats were used for this experiment. The rats with average weight of 181g were randomly assigned into four groups of five each (Groups A, B, C and D). Group A, B and C served as treatments groups while group D as the control. Each rat in the treatment groups A, B and C received 0.1g/kg, 0.15g/kg and 0.20g/kg of monosodium glutamate respectively in 0.5ml of water orally three times daily for two weeks. Result: The histopathological evaluation of the tissues of the ovary showed Infiltration of inflammatory cells in and around the oocyte as well as in the zonal granulosa layer. There was distortion of tissue architecture. Conclusion: MSG alters the histology of the ovary, therefore its consumption should be stopped and to work out safe level of consumption further in depth studies are recommended.


Introduction
Monosodium glutamate (MSG) a sodium salt of naturally occurring (non-essential) L-form of glutamic acid is one of the main flavor enhancer used as an ingredient in various food products 1,2 .It is widely used in restaurants, packaged food industries and household kitchens 3 , in Nigeria, most communities and individuals often use MSG as a bleaching agent for the removal of stains from clothes.MSG is sold in most open market stalls and stores in Nigeria as "Ajinomoto" marketed by West African Seasoning Company Limited 4 or "Vedan" marketed by Mac & Mei (Nig) 5 .Its palatable and favorite flavor is a must in almost all Chinese and South-Asian dishes, where it is known by the names of Ajinomoto, Sasa, Vetsin, Miwon and Weichaun 2 , Limited is a crystalline sodium salt of glutamic acid 5 .MSG improves the taste of food which is called "Umami Taste" in Japanese.It potentiates the activity of gustatory nerves 6,7 , in particular those nerves that mediate sweet taste 8,9 .The effect of MSG is attributed to the presence of the sodium ion, although the glutamate ion by itself can also intensify the activity of gustatory nerves 9 .The effect of MSG on sweet taste is enhanced by guanosine 5'-monophosphate (GMP) 10 .MSG is generally synthesized by a method referred to as microbial fermentation 11,12 .MSG has been reported to causes burning sensation at the back of neck, forearms, chest, facial pressure/tightness, chest pain, headache, nausea, palpitation, numbness in back of neck radiating to arms and back, tingling, warmth, weakness in face, temples, upper back, neck and arms, bronchospasm (observed in asthmatics only), drowsiness, weakness 13 .Bangladesh Journal of Medical Science Vol. 12 No. 04 October '13 The ovary is a paired, egg producing reproductive organ found in female Organism 14 .The ovaries also function in the production of various steroids and peptide hormones like estrogen and progesterone which sub serve many functions in the reproductive system 15 .The aim of this study is to evaluate the effect of MSG on the ovaries.

Animals
The rats were purchased from the Departments of Histopathology Madonna University, Nigeria Elele.The Wistar rats were kept in a clean plastic cages enclosed with wire gauzes cover according to their groups under standard housing conditions at temperature 25 O C-29 O C at a 12hour light and dark cycle.They were fed with growers marsh produced by grand cereals and oil mills limited, Bukuru jos, plateau state, Nigeria, which was obtained from chrys ventures limited, owerri Imo state, Nigeria.

Monosodium glutamate
The powdered form of monosodium glutamate was bought from Elele Market, Rivers State.

Experimental Design /Administration of monosodium glutamate to the Animals
Twenty (20) female adult Wistar rats were used for this experiment.The rats with average weight of 181g were randomly assigned into four groups of five each (Groups A, B, C and D).Group A, B and C served as treatments groups while group D as the control.Each rat in the treatment groups A, B and C received 0.1g/kg, 0.15g/kg and 0.20g/kg of monosodium glutamate respectively in 0.5ml of water orally three times daily for two weeks (fourteen days).The rats were sacrificed on the fifteenth day of the experiment.

Histopathological Examination
The rats were sacrificed 24hrs after the last dose, the ovaries were dissected and fixed in 10% formal saline, dehydrated in ascending grades of alcohol, impregnated and imbedded in paraffin wax.Paraffin sections (5 µm thick) were stained with haematoxylin and eosin (H & E) as a routine stain.This study was approved by local ethical committee.

Weight of Animal
In group A there was a decrease in weight both in week one and two.Group B, the weight in week one was elevated but dropped in the second week .The group C weight was not altered.There were no significantly differences in all the groups compared with the control.

Histopathology
The histopathological evaluation of the tissues of the ovary showed Infiltration of inflammatory cells in and around the oocyte as well as in the zonal granulosa layer.There was distortion of tissue architecture.Nigeria, now NAFDAC has also expressed the view that MSG is not injurious to health 26 .The safety of MSG usage has been generated much controversy locally and globally 27,28 , as earlier stated.

Groups
Our result indicated that at the various doses administered there were no significantly differences in weight in all the groups compared with the control, which is an indication that MSG has little or nothing to do with the body weight.
Histologically the ovary shows infiltration of inflammatory cells in and around the oocyte as well as in the zonal granulosa layer according to their dosage, there was also distortion of tissue architecture.Our results indicate that MSG causes infiltration of inflammatory cells in the ovary, although it may be dose dependent.This study similar to the study carried out by Eweka et al 4 on the histological studies of the effects of monosodium glutamate on the fallopian tubes of adult female Wistar rats, where cellular hypertrophy of the columnar epithelium, distortion of the basement membrane, vacuolations of the fallopian tubes as well as degenerative and atrophic changes, which was attributed to consumption of MSG 27-29 .Although the report of Das and Ghosh 30 on the Long term effects in ovaries of the adult mice following exposure to Monosodium glutamate during neonatal life -a histological study did show any tissue distortion in dosage of 2mg.
Our result is also similar to Eweka A and Om'iniabohs 31 where cellular hypertrophy, degenerative and atrophic changes was reported in animals administered with 0.08mg/kg of MSG and also the study done on Assessment of DNA Damage in Testes from Young Wistar Male Rat Treated with MSG, where Ismail 32 reported alterations of the seminiferous tubules which included atrophied tubules, exfoliation of spermatocytes, spermatids, many nuclei of different types of spermatogenesis appeared pyknotic and necrotic, and dilated congested inter tubular blood vessels, while Mohamed 33 reported that the treatment with MSG at short-term exhibited slight to moderate damaged seminiferous tubules, included vacuoles were found inside the cytoplasm of spermatogonia and loss of late spermatids, shrinkage, widening of the spaces between the tubules.Long-term treatment caused severe damage of germ cells and large masses of necrotic cells were present in many tubules.Focusing on exfoliated, sloughing early spermatids and vacuolation in some damage of seminiferous tubules proved the presence of many signs of deterioration of these cells of tubules.

Conclusion
Based on the present and previously reported studies of MSG on the reproductive system of male and female, it is obvious that MSG exerts deleterious effects.Therefore its consumption should be stopped and to work out tolerable dose further in depth studies involving molecular tools are recommended.
Infiltration of Inflammatory Cells in the Ovary Following Oral Administration of Monosodium Glutamate

Fig. 1 :
Fig.1: Body weight of the three groups experimental rats administered with different doses of Monosodium Glutamate

Table 1 :
Body weight of the three groups experimental rats administered with different doses of Monosodium Glutamate Each value represents the mean±standard deviation (n=5), values are statistically not different from Initial weight.One-way analysis of variance (ANOVA)+ Tukey-Kramer Multiple Comparisons Test