Enhanced uridine adenosine tetraphosphate-induced contraction in renal artery from type 2 diabetic Goto-Kakizaki rats due to activated cyclooxygenase/thromboxane receptor axis

The dinucleotide uridine adenosine tetraphosphate (Up(4)A), which has both purine and pyrimidine moieties, was reported as a novel endothelium-derived contracting factor. Recently, growing evidence has suggested that Up(4)A plays an important role in regulation of the cardiovascular function. We previously demonstrated that Up(4)A-induced vasoconstrictions are altered in arteries from DOCA-salt hypertensive rats. We have assessed responses to Up(4)A shown by renal arteries from type 2 diabetic Goto-Kakizaki (GK) rats (42-46 weeks old) and identified the molecular mechanisms involved. Concentration-dependent contractions to Up(4)A were greater in renal arterial rings from the GK than age-matched control Wistar group. In both groups, the inhibition of nitric oxide synthase (with N-G-nitro-L-arginine) increased the response to Up(4)A, whereas the inhibition of cyclooxygenase (COX) (with indomethacin) decreased the response. Specific inhibitors of COX-1 (valeroyl salicylate) and COX-2 (NS398), a thromboxane (TX) receptor (TP) antagonist (SQ29548), and P2 receptor antagonist (suramin) also decreased the response to Up(4)A. Protein expressions of COXs in renal arteries were greater in the GK than Wistar group. The production of TXB2 (a metabolite of TXA(2)) by Up(4)A did not differ between these groups. Concentration-dependent contractions to U46619, an agonist of the TP receptor, were greater in renal arteries from the GK than Wistar group. The expression of P2X(1) and P2Y(2) receptors did not differ between these groups. These results suggest that enhancement of the Up(4)A-induced contraction in renal arteries from GK rats may be attributable to the increased activation of COXs/TP receptor signaling.