CHANGES IN RAT CORNEAL MATRIX METALLOPROTEINASES AND SERINE PROTEINASES UNDER VITAMIN-A-DEFICIENCY

Purpose. Vitamin A deficiency alters the transparency of the cornea du e to epithelial cell keratinization and increases the susceptibility o f the cornea to ulceration. The purpose of this study was to determine the effect of vitamin A deficiency on rat corneal matrix metalloprote inases and serine proteinases. Methods. Four dietary groups of male WA G/RijMCW rats were prepared: (1) Vitamin A deficient rats were raised on a casein-based retinoid deficient diet; (2) Retinol repleted rats w ere raised on the retinoid deficient diet. On the eighty-sixth day on this diet, the rats were fed retinyl palmitate and then given free acc ess to the retinyl palmitate-supplemented control diet; (3) The weight -matched, pair-fed rats were restricted in their intake of the retinyl palmitate-supplemented diet so that their weight gain matched that of the A- rats; (4) The non-restricted rats were given free access to th e retinyl palmitate-supplemented diet. The animals were killed at the late plateau stage for weight of the deficiency (102-106 days). Zymogr aphy was used to study proteinases in the corneal extracts. Results. V itamin A deficient and control rat corneas contain multiple matrix met alloproteinases and serine proteinases. The matrix metalloproteinases at 90/92 kDa (gelatinase B) and 66/63/57 kDa (gelatinase A) were signi ficantly decreased in the corneas of the vitamin A deficient rats rela tive to the control corneas. Corneas from the four groups of rats cont ained 76, 45, 38, 28 and 22 kDa proteinases that cleaved casein. Only the vitamin A deficient corneas contained a 50 kDa casein cleaving enz yme. The 76, 45, 38 and 28 kDa serine proteinases were significantly l ower in the vitamin A deficient corneas. The major 22 kDa enzyme was n ot altered by the deficiency. All casein cleaving proteinases were inh ibited by phenylmethylsulfonyl fluoride and chymostatin except for a m inor 76 kDa band. The activity of this band was not altered by inhibit ors for the other classes of proteinases, ethylenediaminetetraacetic a cid, E-64 or pepstatin. The concentrations of the 61, 52 and 40 kDa pl asminogen activators were not altered by the deficiency. Conclusions. Alterations in corneal proteinases under vitamin A deficiency conditio ns may be involved in the characteristic changes observed in the corne a under vitamin A deficiency conditions: decreased exfoliation of epit helial cells, increased levels of keratofibrils in the corneal keratoc ytes, increased stromal keratocyte degradation and increased susceptib ility towards ulceration.