Investigation of the Effects of Monosodium Glutamate on the Embryonic Development of the Eye in Chickens

SIMPLE SUMMARY: Monosodium glutamate (MSG, E62, C5H8NO4Na) is the most widely used food additive in the world for enhancing flavour. The number of flavour-enhancers added to foods is very important for the health of consumers. It has been determined by many researchers that MSG has negative effects on various organs of the body. Since chicken embryos develop without the influence of the maternal organism and allow toxicity to be evaluated very quickly and precisely, they have become a preferred experimental model for investigating the embryotoxic and teratogenic effects of chemicals, toxins, drugs, and numerous food additives and flavour-enhancing agents. This study aimed to investigate the effects of in ovo MSG administration at different doses on the embryonic development of the eye using histological and histometric techniques. The results of the present work have shown that in ovo-administered MSG can adversely affect embryonic eye development. ABSTRACT: MSG is the most ubiquitous food additive in the food industry. The aim of this report was to investigate the effects of in ovo MSG administration on embryonic chicken eye development using histological and histometric methods. A total of 410 fertilized eggs obtained from Babcock Brown laying hens (Gallus gallus domesticus) were used and divided into 5 groups: I (untreated control), II (vehicle control), III (0.12 mg/g egg MSG), IV (0.6 mg/g egg MSG), and V (1.2 mg/g egg MSG), and injections were performed via the egg yolk. At incubation day 15, 18, and 21, 6 embryos from each group were sacrificed by decapitation and pieces of eye tissue were obtained. In all MSG groups, it was determined that both corneal epithelium thickness and total corneal thickness decreased at incubation time points 15, 18, and 21 days compared with the controls (p < 0.05). The total retinal thickness, thickness of the outer nuclear layer (ONL), inner nuclear layer (INL), ganglion cell layer (GL), and nerve fibre layers (NFL), as well as the number of ganglion cells decreased significantly at incubation days 15, 18, and 21 (p < 0.05), and degenerative changes such as vacuolar degeneration and retinal pigment epithelial detachment were also observed. In conclusion, MSG in ovo administration can affect the cornea and distinct layers of retinal cells.