|Year : 1988 | Volume
| Issue : 3 | Page : 126-127
Amino acids in retinitis pigmentosa
Department of Ophthalmology, Institute of Medical Sciences, Banaras Hindu University, Varanasi - 221 005, India
M K Singh
Department of Ophthalmology, Institute of Medical Sciences, Banaras Hindu University, Varanasi - 221 005
Retinitis pigmentosa may be associated with amino acid' disorders; whether the association is incidental or consequential is not known. The present investigation on amino acids in retinitis pigmentosa indicates that the level of plasma amino acids does not differ significantly in patients with retinitis pigmentosa compared to that of normal subjects, hence it has no etiological bearing.
|How to cite this article:|
Singh M K. Amino acids in retinitis pigmentosa. Indian J Ophthalmol 1988;36:126-7
| Introduction|| |
Retinitis pigmentosa is a slowly progressive retinal degeneration commencing with night blindness. Histopathologically, there is a primary degeneration of the rods and cones and secondary migration of pigment from the pigment epithelium into the inner retinal layers. The disease has a hereditary trait, the most common mode of inheritence being recessive. Retinitis pigmentosa has an obscure aetiology. Several theories of its causation have been advanced but none. has yet received a universal acceptance. The presence of aminoaciduria in cases of retinitis pigmentosa has encouraged biochemical investigations in the hope of eventually answering a key question; what is the fundamental defect in the disorder? Amino acid disorders like a decrease of plasma taurine, an increase in plasma ornithine,  and a low taurine content in platelets,  were reported in retinitis pigmentosa. However, other investigators , found normal pattern of plasma amino acids in retinitis pigmentosa.
In view of these conflicting reports, the present study was carried out to investigate the pattern of plasma amino acids in patients with retinitis pigmentosa.
| Material and Methods|| |
The investigation was carried out on 16 patients with retinitis pigmentosa and 12 healthy subjects selected consecutively. The diagnosis of retinitis pigmentosa was based on the history of night blindness, the presence of a waxy disc, attenuation of retinal arteries and bone spicule-shaped retinal pigmentary deposits and constriction of visual fields. The patient had no other ocular or systemic disease. The age and sex distribution of the patients and healthy subjects was evenly matched.
Plasma amino acids estimation was carried out by the Whitehead method in which the amino acids were separated by uni-dimensional paper chromatography. Bands on the upper half of the paper chromatogram represented essential amino acids and on the lower half non-essential amino acids. The optical densities of essential and non-essential amino acids were measured at 509 nm with the help of a spectrometer using plain methanol as a blank. The readings obtained from healthy subjects and retinitis pigmentosa patients were subjected to statistical analysis.
| Observations|| |
The amino acid levels in healthy subjects and in patients with retinitis pigmentosa are shown in the table. The ratio of non-essential/essential (NE/E) in control and diseased group were 2.0675± 0.1875 and 2.0594± 0.1771 respectively. The difference in the optical densities of essential and non-essential amino acids and their ratio in normal and retinitis pigmentosa patients is found to be statistically insignificant (7 0. 90).
| Discussion|| |
It has been suggested that certain amino acids have a capacity to augment the regeneration of visual purple and thereby significantly influence the retinal function.  Our investigation on patients with retinitis pigmentosa revealed that the mean values of optical densities of essential and non-essential amino acids and their ratios did not differ significantly from that of healthy subjects. This is in conformity with the earlier reports of Campbell and Tonks.  Our observations do not suscribe to the observation of Berson et al.  who reported deviating values of different amino acids in the plasma of patients with retinitis pigmentosa. Further, Ehlers [4 ] too did not find any difference from the reference values of the levels of tyrosine and phenylalanine - the precursors of pigments in patients with tapeto _retinal clegenerations. The assosication of aminoaciduria with retinitis pigmentosa may be accidental and perhaps it has no consequent influence of the etiology of the disease.
| References|| |
|1.||Berson, E.L., Schmidt, S.Y., Rabin, A.R.,: Plasma amino acids in hereditary retinal disease : Ornithine, Lysine and Taurine. Brit. J. Ophthal., 60 : 142, 1976. |
|2.||Airaksen, E.M. Airaksinen, M.M. et al.: Uptake of taurine by platelets in retinitis pigmentosa. Lancet. 1 : 474-475, 1979. |
|3.||Campbell, D.A. and Tonks, E.L.: Biochemical findings in human retinits pigmentosa with particular reference to vitamin A deficiency. Brit. J. Ophthal., 46 : 151, 1962. |
|4.||Ehlers, N.: Aqueous humour and plasma amino acids in tapeto-retinal degenerations. Acta Ophthal., 59 : 576, 1981. |
|5.||Omayada, K. Acta Soc. Ophthal. Jap., 61 : 432, 1957. |
[Figure - 1]
[Table - 1]