On the recovery of the electroretinogram after removal of intravitreal zinc particles

Effects of vitamin E and pinoline on retinal lipid peroxidation

BACKGROUND

Pinoline is a pineal indoleamine naturally found in the retina. This study compared the effects of pinoline and vitamin E on the copper (I)-induced retinal lipid peroxidation (LPO).

METHODS

Porcine retinal homogenates were mixed with 120 micro M copper (I) solution. The mixtures were co-incubated with various concentrations of pinoline or trolox (water-soluble vitamin E analogue) at 37 degrees Centigrade for 60 minutes. The amounts of malondialdehyde (MDA) and protein were assayed to quantify the LPO.

RESULTS

Copper (I) ions significantly increased the MDA concentration in the retinal homogenates (p < 0.0007). Both pinoline and trolox significantly suppressed MDA in a dose-dependent manner (p < 0.0001) and their effects were significantly different (p = 0.004). The concentrations that inhibited 50 per cent of LPO were 0.24 mM and 0.68 mM for pinoline and trolox, respectively.

DISCUSSION

Pinoline suppressed the LPO at a potency of 2.8 times compared with trolox. The results support an anti-oxidative role for pinoline in the retina. Further study is required to characterise the pharmacological potency of pinoline in vivo.

N-acetyl-serotonin reduces copper (I) ion-induced lipid peroxidation in bovine retinal homogenates

PURPOSE

Chalcosis is an ocular condition caused by penetration injury of copper or its alloy, which leads to extensive ocular inflammation. N-acetyl-serotonin has recently been identified as a potent antioxidant against free radical stress. In this study, we determined the efficacy of N-acetyl-serotonin against the copper (I)-induced retinal lipid peroxidation.

METHODS

Copper (I)-treated (100 microM) bovine retinal homogenates were incubated with 6 different concentrations (i.e. 0.00, 0.25, 0.50, 1.00, 2.00 and 4.00 mM) of N-acetyl-serotonin or vitamin E. The malondialdehyde level was measured as an index of lipid peroxidation.

RESULTS

Copper (I) ions induced a significant dose-dependent increase in malondialdehyde (p=0.007). Co-incubation with N-acetyl-serotonin or vitamin E significantly suppressed the copper (I)-induced malondialdehyde production (p<0.0001). The concentration to inhibit 50% of damage for N-acetyl-serotonin and vitamin E were found to be 1.54 mM and 0.45 mM, respectively.

CONCLUSION

Although N-acetyl-serotonin is only 29% as effective as vitamin E in suppressing the copper (I)-induced lipid peroxidation, the present study supports a pharmacological potential of N-acetyl-serotonin combating free radical oxidative damages in the ocular tissues.

On the recovery of the electroretinogram after removal of intravitreal copper particles

This report details the influence of the time lapse and surface area size of intravitreal copper foreign bodies on the electroretinogram (ERG) and the recovery of the potentials after removal of the particles. Pure copper wires were implanted temporarily into the vitreous body of rat eyes in the area of the ora serrata and the values of the ERG were compared with those of the intact fellow eyes. In three different procedures with groups of 12 animals each the following results were obtained: (1) The metal toxicity of small copper particles (0.3 mm2) remaining one day in the vitreous body reduced the amplitudes of the a1-, a2-, and b-wave only 10% by the end of the observation time of 260 days, (2) The loss of ERG amplitudes increased to about 25% under the influence of larger copper particles (1.3 mm2; time lapse one day); and (3) Copper particles with an active surface of 1.3 mm2 remaining two days in the vitreous body caused a permanent loss of about 50%.

On the recovery of the electroretinogram of rats after removal of intravitreal lead particles

Lead particles (1.4 mm2) were implanted into the vitreous body of rats (16 animals) for 10 days and the recovery rate of the ERG was measured over an observation time of 190 days. After extraction of the lead particles the a- and b-wave amplitudes show a recovery from about 60% to 87% in comparison to those of the intact fellow eyes between the 60th and 90th day of observation. In earlier experiments the mechanical damage was measured using glass splinters. The differences between these values and the above mentioned recovery rate after lead extraction correspond to the irreversible component of the metal intoxication. In another group of rats (16 animals) the lead particle was not removed before the end of the observation time of 190 days. Subtracting these ERG values from those of the first group of rats after lead extraction one gets small differences which correspond to the reversible component of the metal intoxication. The irreversible lead intoxication is much less than that of intravitreal iron particles as we found under the same conditions. The lead particles we used, are larger than those we have to handle in clinical cases taking the relation of surface area size of the particle to the total bulbus weight. The ophthalmoscopical findings are described.