[Response of the coronary arteries to cold test and flow velocity increase is improved by deferoxamine but not by L-arginine in diabetic patients].

Unlabelled: Acetylcholine produces coronary artery (CA) constriction in diabetic patients suggesting an impairment of endothelium-dependent dilation. To examine the mechanism of this abnormal response. 2 physiological tests, i.e. cold pressor test (CPT) and coronary flow-increase induced by 10 mg papaverine (PAP) injection in the distal left anterior descending CA (dLAD), were performed before (1) and after (2) either i.v. L-arginine (L-arg, 625 mg/min x 10 min) or i.v. desferrioxamine (DFX, 50 mg/min x 10 min) in 15 normotensive nonsmoker diabetic patients with angiographically normal CA and normal cholesterol. Dimensions of the proximal LAD (pLAD) were measured by quantitative angiography. [table: see text] Before administration of L-arg or DFX, CPT induced a decrease of pLAD diameter, and PAP injection in dLAD dit not modify pLAD diameter. In the 7 diabetic patients receiving L-arg, responses to CPT and PAP were not modified. Conversely in the 10 patients receiving DFX, pLAD dilated in response to the 2 tests. Intracoronary isosorbide dinitrate, an endothelium-independent dilator, produced similar dilation in the 2 groups (+20 +/- 8% and +16 +/- 6%, respectively).

Conclusions: 1) responses of angiography normal CA to CPT and to flow increase are impaired in diabetic patients; 2) abnormal responses are not improved by L-arg suggesting that a deficit in substrate for NO synthesis is not involved; 3) DFX restores a vasodilator response to the 2 tests suggesting that inactivation of NO by superoxide radicals might be partly responsible of the impairment of CA dilatation in diabetic patients.