EFFECTS OF NON-INSULIN-DEPENDENT DIABETES-MELLITUS ON THE REACTIVITY OF HUMAN INTERNAL MAMMARY ARTERY AND HUMAN SAPHENOUS-VEIN

The effects of non-insulin-dependent diabetes mellitus (NIDDM) were in vestigated on the reactivity of human internal mammary artery (IMA) an d saphenous vein (SV) rings obtained from coronary artery patients (CA P) undergoing coronary artery bypass surgery. In the presence of endot helium, the maximal contractile response and sensitivity (pot) of IMA or SV to NA and ET-1 significantly increased in CAP with NIDDM relativ e to CAP only (controls). Removal of the endothelium markedly and sign ificantly enhanced the maximal contractile response and sensitivity of IMA or SV to NA in CAP only, but did not induce a significant alterat ion in CAP with NIDDM compared to that in the presence of endothelium. The maximal contractile response and sensitivity of diabetic vessels with or without endothelium to NA were similar to values of correspond ing vessels without endothelium obtained from nondiabetic CAP. The max imum contractions developed by NA or ET-1 were much greater in SV than that determinated in the IMA. Acetylcholine (ACh) and histamine produ ced endothelium-dependent relaxations in precontracted IMA and these e ffects of ACh and histamine significantly decreased in CAP with NIDDM. Endothelium-dependent relaxations stimulated by ACh were more pronoun ced in IMA than that determinated in the SV. In precontracted SV, hist amine induced marked contractions that were significantly greater in C AP with NIDDM relative to CAP only. Endothelium-independent relaxation s of vessels to sodium nitroprusside (SNP) were not influenced by NIDD M. Data indicate that NIDDM causes a deficit in the vasorelaxant activ ity of endothelium, leading to an increase in contractility of human I MA and SV. Data also suggest that IMA can be a better choice of graft for coronary occlusive disease than SV, specially in patients with NID DM.