Abstract 1470: Endothelial Specific Overexpression of the L-Arginine Transporter, CAT1, Augments Nitric Oxide Production and Endothelial Function
Background: Endothelial dysfunction due to reduced nitric oxide (NO) bioavailability is a fundamental feature of a number of cardiovascular disorders and their associated risk factor states. Several mechanisms have been proposed to account for the diminution in NO availability. Recently we demonstrated in patients with hypertension and heart failure that there was a reduction in uptake of the NO precursor, L-arginine.
Methods and Results To demonstrate whether endothelial arginine transport could influence NO production we generated a transgenic mouse that overexpresses the key L-arginine transporter, CAT1, in an endothelial specific manner by utilizing a Tie2 promoter-enhancer construct (Tie2-CAT1 tg). Endothelial function was subsequently evaluated in 10 week old mice by mounting aortic rings in a myograph. Responses to acetylcholine were significantly augmented in the Tie2-CAT1 tg compared to littermate controls (-log EC50: 7.49±0.06 vs 6.89±0.06, p<0.01, Figure⇓). To further characterise endothelial function, we isolated endothelial cells from Tie2-CAT1 tg and wild-type aortae by FACS sorting. Uptake of 3H-L-arginine was increased by 25% in Tie2-CAT1 tg mice (p<0.05). In conjunction we determined the rate of release of NO using the NO-sensitive fluorophore DAF2. NO release was significantly increased in Tie2-CAT1 tg endothelial cells: 2.33±0.03 vs 1.80±0.04 RU, p<0.05).
Conclusion: This study firmly establishes the pivotal role that the endothelial L-arginine transporter plays in determining vascular function.