March 1987, Volume 37, Issue 3

Original Article


S. Zarina  ( H.E.J. Research Institute of Chemistry, University of Karachi, Karachi. )
Z.H. Zaidi  ( H.E.J. Research Institute of Chemistry, University of Karachi, Karachi. )
J.H. Wania  ( Anklesaria Hospital and Nursing Home, Garden Road, Karachi. )


Free amino acids content of aqueous humor in Pakistani subjects with senile cataract is measured and results are compared with previous studies Most of the amino acids showed lower concentration than those reported for European’ and American2 subjects (JPMA 37 67, 1987).


Analysis of aqueous humor has been em­ployed as a diagnostic tool in human beings for certain ophthalmic diseases3,4 Aqueous humor is ‘a transudate of plasma and provides the amino acids required for the synthesis of lenticular proteins5 The free amino acids composition in ocular fluids has been studied in rat, cat, monkey6, rabbit7 sheep8 and human1,2,5,9, dIn this study, we report the free amino acid composition of aqueous humor removed during cataract surgery. The results are compared with the previous studies.


Aqueous humor samp1es (100-150 jul) were aspirated from anterior chamber of 13 human subjects (average age 65 years) before removal of the lens. All these had senile cataract uncompli­cated by any other medical or ocular disorder such as diabetes, hypertension, uremia or glaucoma. Proteins were precipitated by addition of 25 U of 10% w/v sulfosalicylic acid to 100-150Ul of aqueous humor. The mixture was shaken vigorou­sly and kept for 30 minutes at 4 °C. Clear super­natent was separated from precipitated protein by centrifugation (3000xg) The free amino acids content were measured in 50Ul protein free aqueous humor using Biotronik amino acid analy­zer LC-6001 (Biotronik-GmbH, Munich, West Germany).


The data presented in Table 1 shows free amino acid composition in aqueous humor of the Pakistani patients. Figure 1 shows a comparison of the previous7 and the present work. In general, most of the amino acids were found to be in lower concentration in the present study except for glycine which was found to be similar (Figure 1).

The levels of proline and citrulline were elevated in Pakistani subjects

(Table II) as compared to American2 subjects. We could not compare these values with that of European1 data as the results for these were not reported.
It is likely that the variation in the composi-tion reflects the different dietary habits of Pakistani population. The Pakistani food contains relatively low animal protein content. Another possible way to explain this deficit is on account of racial differences and ethnic associated conditions, which need to be examined. Whatever the reason be, it is known that amino acids deficiency leads to cataractogenesis10,11s Amino acid deficiency in aqueous humor may initiate, if not cause, the process of cataract formation. Further studies on amino acid composition of lens and plasma from subjects with cataract are in progress and may help in understanding the earlier onset of cataract in Pakistan.


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2. Dickinson, J.C., Durham, D.G. and Hamilton, PJ3. Ion exchange chromatography of free amino acids in aqueous fluid and lens of the human eye. Invest. Ophthalmol., 1968; 7: 551.
3. Barber, G.W. Physiological chemistry of the eye. Arch. Ophthalmol., 1973; 89: 236.
4. Dernouchamps, J.P. The proteins of the aqueous humour. Doc. Ophthalmol., 1982; 53: 193.
5. Barber, G.W. Free amino acids in senile cataractous lenses; possible osmotic etiology. Invest. Ophthalmol., 1968: 7:564.
6. Reddy, D.V.N. Distribution of free amino acids and related compounds in ocular fluids, lens and plasma of various mammalian species. Invest. Ophthalmol., 1967; 6:478.
7. Reddy, D.V., Rosenberg, C. and Kinsey, V.E. Steady state distribution of free amino acids in the aqueous humours, vitreous body and plasma of the rabbit. Exp. Eye Res., 1961; 1:175.
8. Reddy, D.V. Distribution of Nat, K+ and free amino acids in lenses of sheep with erythrocytes containing high and low potassium. Exp. Eye Res., 1972; 14:293.
9. Hanna, C. and Sanchez, J. Effects of acetazolamide on concentration of free amino acids in aqueous humor. Ophthalmic Res., 1972;3: 283.
10. Hall, W.K., Bowles, L.L., Sydenstricker, V.P. and Schmidt, H.L. Jr. Cataracts due to deficiencies of phenyl alanine and of histidine in rat. A comparison with other types of cataracts. J. Nutr., 1948; 36: 277.
11. Bunce, G.E., Caasi, P., Hall, B. and Chaves, N. Prevention of cataract in the progeny of rats fed a maternal diet based on vegetable proteins. Proc. Soc. Exp. Biol. Med., 1972; 140:1103.

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