Relationship between the concentration of copper and iron in the aqueous humour and intraocular pressure in rabbits treated with topical steroids.
OBJECTIVE
To evaluate the concentration of copper and iron in the aqueous humour of steroid-treated eyes, particularly to study the concentration of these metals in relation to steroid-induced increases in intraocular pressure (IOP).


METHODS
Adult rabbits of both sexes were selected in order to study the effect of steroids on the concentrations of copper and iron in the aqueous humour and on IOP. The rabbits were acclimatised for 2 weeks prior to the instillation of various drugs into the eyes. Then a steroid (dexamethasone, betamethasone or fluoromethalone) was instilled in both eyes of the rabbits, for about 1 month. Intraocular pressure was measured twice a week. When IOP was significantly increased, the animals were killed. The aqueous humour was collected and analysed for copper and iron using atomic absorption spectrophotometry coupled with graphite fumace.


RESULTS
After about 30 days of steroid treatment the mean (+/- SD) IOP in dexamethasone, betamethasone and fluoromethalone treated groups was 17.5 (+/- 4.81) mmHg, 18.48 (+/- 4.5) mmHg and 21.8 (+/- 5.7) mmHg, respectively. These values were significantly higher compared to the control group where the mean IOP was 11.6 (+/- 2.2) mmHg. The concentration of copper in the aqueous humour of steroid-treated rabbits was significantly lower (P < 0.001) compared to the control group. However, the concentration of iron was not significantly different between the control and steroid treated rabbits.


CONCLUSIONS
A greater increase in IOP was observed in the fluoromethalone-treated group compared to the dexamethasone and betamethasone-treated groups, but the difference was not significant. The lower concentrations of copper in aqueous humour in steroid-treated eyes may play an important role in the maintenance of IOP. The concentration of iron was not significantly different compared to the control group. These results may help to explain the role of these metals in the pathogenesis of open angle glaucoma.
Iqbal
Zafar
Z
Department of Pharmacy, University of Peshawar, Pakistan. zafariqbal_735@yahoo.com
Muhammad
Zia
Z
Shah
M Tahir
MT
Bashir
Shumaila
S
Khan
Taous
T
Khan
Muhammed Daud
MD
D000287:Administration, Topical; D000818:Animals; D000893:Anti-Inflammatory Agents / Q000494:pharmacology*; D001082:Aqueous Humor / Q000378:metabolism*; D001623:Betamethasone / Q000494:pharmacology; D003300:Copper / Q000378:metabolism*; D003907:Dexamethasone / Q000494:pharmacology; D005260:Female; D005469:Fluorometholone / Q000494:pharmacology; D005938:Glucocorticoids; D007429:Intraocular Pressure / Q000187:drug effects*; D007501:Iron / Q000378:metabolism*; D008297:Male; D009798:Ocular Hypertension / Q000139:chemically induced / Q000378:metabolism*; D011817:Rabbits; D013054:Spectrophotometry, Atomic; D014065:Tonometry, Ocular
D000893:Anti-Inflammatory Agents; D005938:Glucocorticoids; D003300:Copper; D003907:Dexamethasone; D001623:Betamethasone; D007501:Iron; D005469:Fluorometholone