Hyperglycaemia alters the endothelium-dependent relaxation of canine coronary arteries

The aim of the present study was to investigate the effects of experimental diabetes and hyperglycaemia per se on the endothelium-dependent relaxation of isolated canine coronary arteries and to analyse the possible involveme nt of the cyclooxygenase pathway in the alterations induced by hyperglycaem ia. Rings from the left anterior descending coronary arteries of 18 metabol ically healthy, six alloxan-diabetic and six insulin-treated alloxan diabet ic dogs were set up for isometric tension recording. Diabetic coronaries as well as healthy vessels subjected to in vitro hyperglycaemia (25.5 mmol L- 1 glucose) showed impaired (P < 0.05) relaxation to acetylcholine (3 nmol L -1-10 mu mol L-1) compared with normoglycaemic, i.e. metabolically healthy and insulin-treated diabetic controls, either before or after indomethacin (3 mu mol L-1) administration. The maximal dilation elicited by acetylcholi ne was further decreased (P < 0.05) by the cyclooxygenase inhibitor in the diabetic coronaries only. Relaxation to sodium nitroprusside did not differ among groups. These results suggest that hyperglycaemia may result in impa ired endothelium-dependent dilation of coronary arteries. Diminished relaxa tion of diabetic coronaries is worsened by the inhibition of the synthesis of vasodilator cyclooxygenase products.