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M. P. Langford, K. E. Taba, J. L. Croad, J. L. Rains, S. K. Jain; Comparative Analysis of Plasma and Lens Gamma-Glutamyltranspeptidase (GGT) Activity in Type 1 and Type 2 Diabetic Rat Models. Invest. Ophthalmol. Vis. Sci. 2008;49(13):2286.
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© ARVO (1962-2015); The Authors (2016-present)
Elevated GGT is a risk factor for insulin resistance as well as cataract formation. We investigated the hypothesis that a co-ordinate lenticular GGT and glutathione (GSH) response occurs with development of experimental type 1 (T1) and type 2 (T2) diabetes.
T1 diabetes was induced by Streptozocin (STZ) treatment in Sprague-Dawley rats and T2 diabetes developed by 16 weeks in Zucker diabetic fatty (ZDF) rats. The pre- and post diabetic plasma and lens levels of GGT and GSH were compared. Plasma samples and whole lenses were obtained from 8-10 rats prior to and 6 to 8 weeks post diabetes detection. The Accu-Chek® plasma glucose concentration, plasma and lens GGT and GSH levels were determined by standard colorimetric assays.
The GGT activity in the T1 diabetic rat plasma was 5-fold higher (p=0.002) than in control non-diabetic plasma. There was a close association between elevated plasma glucose and increased GGT (r = .0615; slope= 0.534) in STZ diabetic rats. The GGT and GSH levels in T1 diabetic lens were significantly lower (p’s<0.01) than in control non-diabetic lens. The GGT activity in plasma of control ZDF rats was 2-fold lower than in diabetic STZ rats. T2 plasma GGT levels tended to be inversely related to the plasma glucose concentration (r =.0215; slope= -.051). The levels of GGT and GSH in lens were lower in diabetic versus non-diabetic ZDF rats.
The results suggest that the T1 and T2 diabetic rat models are dissimilar with regard to the relationships between elevated plasma glucose and GGT levels. The results suggest that a co-ordinate reduction in GGT and GSH levels occurs in diabetic rat lens.
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