Morphometric assessment of the effects of monosodium glutamate on the carotid sinus wall: an experimental study

The increase in global burden of stroke is hard to overestimate. Every year it continues to be a leading cause of mortality worldwide. Extracranial pathology of the carotid arteries is a major underlying reason of stroke. Given the role of alimentary factors in the development of atherosclerosis of the carotid arteries, possible influence of food additives on the carotid sinus structure is of special interest. Monosodium glutamate is one of the most common food additives that is allowed for consumption in many countries due to it being considered relatively safe. Recent scientific research however points towards the possible adverse effects of monosodium glutamate on the living organism. The aim of this study was to analyze qualitative and quantitative parameters of carotid sinus structural organization of white male albino rats under normal conditions, in the setting of oral monosodium glutamate consumption and after its withdrawal. Carotid sinuses of 30 white male albino rats that had been daily consuming 10 mg/kg of monosodium glutamate for 4 or 8 weeks with subsequent withdrawal for 2 weeks were subjected to qualitative and quantitative analysis at different time-points of the experiment. The data obtained was compared with the results of morphologic and morphometric study of carotid sinuses of 9 rats of the control group. For morphometric analysis, the following parameters were considered: intima thickness, media thickness, adventitia thickness, diameters of the arterioles, venules and capillaries of the carotid sinus vasa vasorum. Summarizing the morphometric analysis results, it is worth noting that, for the duration of 8 weeks of the experiment, steady increase in the thickness of all layers of the vascular wall, but especially intima and adventitia, was observed in the study group. At the same time, the diameter of the arterioles located in the carotid sinus adventitia was decreasing, while venules and capillaries demonstrated invariable increase of their lumen diameter. After 2 weeks of monosodium glutamate withdrawal, the thickness of intima and adventitia continued to increase, while media thickness had somewhat decreased, probably due to fibrosis and dystrophy. The tendency towards narrowing of the arterioles’ lumen and widening of the venules and capillaries persisted for at least 2 weeks despite discontinuation of monosodium glutamate. Therefore, systematic consumption of monosodium glutamate may lead to impairment of carotid sinus structural organization, particularly endothelial proliferation, fibrotic and dystrophic changes of media, adventitia thickening as well as microcirculatory vessels damage, that continue to persist despite the food additive withdrawal.