An arteriograph was used to assess myogenic tone, smooth muscle contractility and the influence of endothelial function on mesenteric resistance artery reactivity in insulin-resistant mice (C57BL/KsJ-db/db) and age- and gender-matched wild-type mice. Increases in transmural pressure induced myogenic tone in arteries from both control and db/db mice. At 12 and 16 weeks of age, greater tone developed in diabetic than in control mice. In control, but not in db/db mice, pretreatment of arteries with L-NAME potentiated myogenic tone. Indomethacin and SQ29548 (PGH₂/TXA₂ receptor antagonist) had no efffect in control, but inhibited myogenic tone in db/db mice. Endothelium-dependent vasodilation induced by acetylcholine and bradykinin, was depressed in db/db mice and potentiated by SQ29548 and LY333531 (protein kinase C_β inhibitor). Messenger RNA expression levels for PKC_β were over-expressed 2.5-fold in db/db relative to those in control mice. However, expression levels of mRNA for eNOS, PKC_α, and PKC_ξ were similar in the db/db and control mice. Collectively, these results suggest that the greater myogenic tone in resistance arteries from diabetic mice may be attributable, to greater amounts of one or more vasoconstricting prostanoids. Our data indicate that in diabetic mice, basal and agonist-stimulated NO releases are depressed and NO-mediated vasorelaxation in these mice may be countered by an endogenous vasoconstrictive prostanoid. This prostanoid-induced vasoconstriction is mediated by a PKC_β-dependent mechanism. Therefore, heightened activation of PKC_β and release of a vasoconstrictor prostanoid could play a role in endothelial dysfunction associated with type II diabetes.

Lessons learned during 1,701 clinical uses of HBOC-201, a polymerized bovine hemoglobin-based oxygen carrier (HBOC), were identified to provide management lessons and training material for future clinical trials and use. HBOC-201 contains 13 g/dL hemoglobin (Hb), is iso-oncotic, stable at 2°C to 30°C with shelf-life of 3 years, requires no cross-matching with half-life of 19 h, and plasma volume distribution. Adverse effects include increased blood pressure, oliguria, gastrointestinal (GI) symptoms, yellow skin and scleral discoloration, decreased pulse oximetry measurements, and transient increases in methemoglobin, hepatic, and pancreatic enzymes. There was no cardiotoxicity. Elevations in blood pressure were transient and were managed with vasodilators. Oliguria was of limited duration. GI symptoms were treated with smooth muscle relaxants. Yellow skin and sclera were self-limiting, caused by Hb metabolism. The most important clinical management errors were lack of understanding of volume expansion effects and the half-life properties of HBOC-201, and failure to repeat infusions. Early use of HBOC-201 for Expanded Access when Hb less than 5 g/dL optimized survival and minimized advanced resource utilization. For phase 3 trials, there was transfusion avoidance of 96% for 24 h, 70% for 1 week, with no difference in serious adverse events or mortality whether patients received at most 10 bags HBOC-201 or at most 3 units blood. More nonserious events occurred with HBOC-201. Age, history of cardiac disease, and Hb deficit, but not randomization to HBOC-201, were significantly predictive of cardiac ischemic events. Administration of HBOC-201 in1,701 humans showed it was well tolerated in a wide range of doses and clinical settings. HBOC-201 should be considered when blood is not available or an option.

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Nitric oxide (NO) exerts a wide range of cellular effects in the cardiovascular system. NO is short lived, but S-nitrosoglutathione (GSNO) functions as a stable intracellular bioavailable NO pool. Accordingly, increased levels can facilitate NO-mediated processes, and conversely, catabolism of GSNO by the regulatory enzyme GSNO reductase (GSNOR) can impair these processes. Because dysregulated GSNOR can interfere with processes relevant to cardiovascular health, it follows that inhibition of GSNOR may be beneficial. However, the effect of GSNOR inhibition on vascular activity is unknown. To study the effects of GSNOR inhibition on endothelial function, we treated rats with a small-molecule inhibitor of GSNOR (N6338) that has vasodilatory effects on isolated aortic rings and assessed effects on arterial flow-mediated dilation (FMD), an NO-dependent process. GSNOR inhibition with a single intravenous dose of N6338 preserved FMD (15.3 ± 5.4 vs. 14.2 ± 6.3%, P = nonsignificant) under partial NO synthase inhibition that normally reduces FMD by roughly 50% (14.1 ± 2.9 vs. 7.6 ± 4.4%, P < 0.05). In hypertensive rats, daily oral administration of N6338 for 14 days reduced blood pressure (170.0 ± 5.3/122.7 ± 6.4 vs. 203.8 ± 1.9/143.7 ± 7.5 mmHg for vehicle, P < 0.001) and vascular resistance index (1.5 ± 0.4 vs. 3.2 ± 1.0 mmHg · min · l(-1) for vehicle, P < 0.001), and restored FMD from an initially impaired state (7.4 ± 1.7%, day 0) to a level (13.0 ± 3.1%, day 14, P < 0.001) similar to that observed in normotensive rats. N6338 also reversed the pathological kidney changes exhibited by the hypertensive rats. GSNOR inhibition preserves FMD under conditions of impaired NO production and protects against both microvascular and conduit artery dysfunction in a model of hypertension.

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