Direct assessment and diminished production of morphine stimulated NO by diabetic endothelium from saphenous vein

• Published in: Acta pharmacologica Sinica Vol. 23; no. 2; pp. 97 - 102
• Main Authors: Bilfinger, Thomas V, Vosswinkel, James A, Cadet, Patrick, Rialas, Christos M, Magazine, Harold I, Stefano, George B
• Format: Journal Article
• Language: English
• Published: United States 01.02.2002
• Subjects: Aged; Diabetes Mellitus, Type 2 - metabolism; Diabetes Mellitus, Type 2 - pathology; Endothelium, Vascular - drug effects; Endothelium, Vascular - metabolism; Female; Humans; Male; Middle Aged; Morphine - pharmacology; Nitric Oxide - metabolism; Nitric Oxide Synthase - metabolism; Receptors, Opioid, mu - metabolism; Saphenous Vein - cytology
• ISSN: 1671-4083

To directly measure in real time basal and stimulated levels of NO released from human saphenous vein endothelium and to quantify the expression of the mu opiate receptor, which has been linked with NO release. Saphenous vein segments from patients with type 2 diabetes (n=12) and patients without diabetes (n=8) were obtained. The release of NO was measured directly from the endothelium using a NO-specific amperometric probe. N(Omega)-nitro-L-arginine methyl ester (L-NAME, 0.1 mmol/L), a NO synthase (NOS) inhibitor, or morphine (1 mumol/L), a stimulant, was administered and the measurements were repeated. Values were reported relative to the mean initial measurement of NO release from diabetic endothelium, which was defined as the relative zero level of NO release. A RT-PCR was then performed on the endothelium to measure mu opiate receptor expression. Diabetic patients (n=12) showed a relative and significantly diminished basal level of released NO, (0.049+/-0.012) nmol/L, compared with non diabetic patients (n=8), (0.42+/-0.12) nmol/L (P<0.05). Application of L-NAME to nonstimulated tissues resulted in no change in NO release from the diabetic group and a decrease in NO release of (0.21+/-0.09) nmol/L from the non diabetic group (P<0.05). Morphine stimulation of the diabetic endothelium resulted in a lower peak and shorter duration of NO release compared to the non-diabetic tissue, (21+/-6) nmol/L vs (38+/-4) nmol/L and (7.3+/-1.4) min vs (12.2+/-2.2) min, respectively (P<0.01). Lastly, evaluation of the mu opiate receptor expression was found to be diminished in the diabetics by 59.1 %. Maturity-onset diabetes attenuates both the constitutive basal and morphine stimulated NO release from human saphenous vein endothelium. In this study, after NOS inhibition, the actual basal NO release in diabetes was negligible. One explanation for the impaired capacity of diabetic endothelium to release NO was the diminished mu opiate receptor that was seen in diabetic endothelium.