Late ultrastructural changes in the rat chorioretinal complex following injection of mixture of 40% ethanol and 100% methanol

Abstract

Background: Consumption of surrogate alcohol containing methanol may result in blindness and even death. The literature is scant on experimental and especially morphological studies on the effect of surrogate alcohol containing methanol and ethanol on organs (particularly, the eye) and tissues of experimental animals.

Purpose: To examine late ultrastructural changes in the interplay of cells of the rat chorioretinal complex (endothelial cells of the choriocapillaries, retinal pigment epithelium (RPE) cells, and photoreceptor cells) following a single intraperitoneal (IP) injection of alcohol mixture (40% ethanol and 100% methanol) at the proportion of 3:1, with a methanol dose of 2.5 g/kg.

Material and Methods: Twelve adult Wistar rats (weight, 250-300 g) were divided into two groups, each of 6 rabbits. Group 1 (the experimental group) received a single IP injection of alcohol mixture (40% ethanol and 100% methanol) at the proportion of 3:1, with a methanol dose of 2.5 g/kg, whereas group 2 (controls) received a single IP injection of 100% methanol at a dose of 2.5 g/kg. The LD50 value for IP administration of methanol in rats is reported as 9.5 g/kg body weight. The ultrastructure of endothelial cells of the choriocapillaries, RPE cells, and photoreceptor cells was examined on a PEM-100-01 Transmission Electron Microscope (Selmi, Sumy, Ukraine) at 1 and 3 months after IP injection of the above alcohol mixture in rats.

Results: At one month after IP injection of the alcohol mixture, the lumen of the choroidal capillaries and ground substance of the Bruch’s membrane appeared osmiophilic, indicating increased lipid levels. In most choroidal capillaries, endothelial cells exhibited signs of hydropic degeneration. The RPE cells showed polymorphic changes; some of them showed severe degeneration of organelles, sometimes with total loss of cytoplasm and damage to the plasmalemma at the basal and apical surfaces; some other RPE cells showed signs of compensatory and restorative processes aimed at intracellular repair processes. There were signs of intercellular and intracellular edema and degeneration of membrane structure in the photoreceptor cell layer. At 3 months after IP injection of the alcohol mixture, signs of hydropic degeneration in the examined structures of the chorioretinal complex were somewhat less severe than at the previous time point. A long-term toxic effect of consuming a small dose of methanol was characterized by severe pathologic changes in and poor reserve potential of the cells of the chorioretinal complex, which was reflected in slow repair processes during the period from 1-month to 3-month time points. This likely explains the reported cases of a prolonged serious condition of individuals after consuming surrogate alcohol. 

Conclusion: A single IP injection of the alcohol mixture with a methanol dose of 2.5 g/kg body weight resulted both in signs of hydropic degeneration and slow repair processes in the cells of the rat chorioretinal complex during the period from 1-month to 3-month time points. A single IP injection of pure methanol (2.5 g/kg) resulted in uniform and more severe changes in the cells of the rat chorioretinal complex. Methanol can be attributed a leading role in the development of pathological changes in the examined structures of the chorioretinal complex after injection of the alcohol mixture.