Citations

Cationic polypeptides are released by activated leukocytes and may play an important role in the regulation of vascular tone. Effects of cationic polypeptides on cerebral vascular tone have not been studied. The present experiments were designed to determine if synthetic cationic polypeptides, poly-L-arginine and poly-L-lysine, affect the function of cerebral arteries. Rings of canine basilar arteries with and without endothelium were suspended for isometric force recording. Poly-L-arginine (10 –8 –10 –7 M) and poly-L-lysine (10 –8 –10 –7 M) caused endothelium-dependent relaxations. A nitric oxide synthase inhibitor, N G -nitro-L-arginine methyl ester (10 –4 M), and a nitric oxide scavenger, oxyhemoglobin (3 × 10 –6 M), inhibited relaxations in response to cationic polypeptides. Negatively charged molecules, heparin (1 U/ml) and dextran sulfate (10 mg/ml), also inhibited relaxations to poly-L-arginine or poly-L-lysine. Higher concentrations of poly-L-arginine (10 –6 –10 –5 M) and poly-L-lysine (10 –6 –10 –5 M) induced endothelium-independent contractions. A protein kinase C inhibitor, staurosporine (10 –8 M), abolished these contractions. Heparin (10 U/ml) and dextran sulfate (100 mg/ml) inhibited the contractile effect of cationic polypeptides but did not affect contractions to phorbol 12,13-dibutyrate. Poly-L-arginine (10 –6 M) and poly-L-lysine (10 –6 M) abolished endothelium-dependent relaxations in response to bradykinin (10 –10 –10 –6 M) or calcium ionophore A23187 (10 –9 –10 –6 M). Heparin (50 U/ml) and dextran sulfate (200 mg/ml) restored endothelium-dependent relaxations to bradykinin (10 –10 –10 –6 M) in arteries exposed to poly-L-arginine (10 –6 M) or poly-L-lysine (10 –6 M). These studies demonstrate that in the lower concentration range (10 –8 –10 –7 M), poly-L-arginine and poly-L-lysine induce endothelium-dependent relaxations by production of nitric oxide via charge-dependent activation of endothelial nitric oxide synthase. In the higher concentration range (10 –6 –10 –5 M), cationic polypeptides cause endothelium-independent contractions as well as impairment of endothelium-dependent relaxations in response to bradykinin and A23187. These contractions and inhibition of endothelium-dependent relaxations are also mediated by a charge-dependent mechanism and may involve activation of protein kinase C.

Background Septic shock is associated with vasopressin deficiency and a hypersensitivity to its exogenous administration. The goal of the current study was to determine whether short-term vasopressin infusion in patients experiencing severe septic shock has a vasopressor sparing effect while maintaining hemodynamic stability and adequate end-organ perfusion. Methods Patients experiencing septic shock that required high-dose vasopressor support were randomized to a double-blinded 4-h infusion of either norepinephrine (n = 11) or vasopressin (n = 13), and open-label vasopressors were titrated to maintain blood pressure. To assess end-organ perfusion, urine output and creatinine clearance, gastric mucosal carbon dioxide tension, and electrocardiogram ST segment position were measured. Results Patients randomized to norepinephrine went from a median prestudy norepinephrine infusion of 20.0 microg/min to a blinded infusion of 17.0 mug/min at 4 h, whereas those randomized to vasopressin went from a median prestudy norepinephrine infusion of 25.0 microg/min to 5.3 microg/min at 4 h (P < 0.001). Mean arterial pressure and cardiac index were maintained in both groups. Urine output did not change in the norepinephrine group (median, 25 to 15 ml/h) but increased substantially in the vasopressin group (median, 32.5 to 65 ml/h; P < 0.05). Similarly, creatinine clearance did not change in the norepinephrine group but increased by 75% in the vasopressin group (P < 0.05). Gastric mucosal carbon dioxide tension and electrocardiogram ST segments did not change significantly in either group. Conclusions The authors conclude that short-term vasopressin infusion spared conventional vasopressor use and improved some measures of renal function in patients with severe septic shock.

Background— Adrenergic activation is thought to be an important determinant of outcome in subjects with chronic heart failure (CHF), but baseline or serial changes in adrenergic activity have not been previously investigated in a large patient sample treated with a powerful antiadrenergic agent. Methods and Results— Systemic venous norepinephrine was measured at baseline, 3 months, and 12 months in the β-Blocker Evaluation of Survival Trial (BEST), which compared placebo treatment with the β-blocker/sympatholytic agent bucindolol. Baseline norepinephrine level was associated with a progressive increase in rates of death or death plus CHF hospitalization that was independent of treatment group. On multivariate analysis, baseline norepinephrine was also a highly significant ( P <0.001) independent predictor of death. In contrast, the relation of the change in norepinephrine at 3 months to subsequent clinical outcomes was complex and treatment group-dependent. In the placebo-treated group but not in the bucindolol-treated group, marked norepinephrine increase at 3 months was associated with increased subsequent risks of death or death plus CHF hospitalization. In the bucindolol-treated group but not in the placebo-treated group, the 1st quartile of marked norepinephrine reduction was associated with an increased mortality risk. A likelihood-based method indicated that 18% of the bucindolol group but only 1% of the placebo group were at an increased risk for death related to marked reduction in norepinephrine at 3 months. Conclusions— In BEST, a subset of patients treated with bucindolol had an increased risk of death as the result of sympatholysis, which compromised the efficacy of this third-generation β-blocker.

Upper body obesity is associated with insulin resistance, hypertension, and endothelial dysfunction. We examined forearm vascular function in response to vasodilator (endothelium-dependent and endothelium-independent) and vasoconstrictor stimuli in 8 normotensive, upper body/viscerally obese men with a positive family history of hypertension and 8 age-matched nonobese men. We also measured body composition and insulin regulation of free fatty acid (FFA) and glucose metabolism. Forearm blood flow was measured before and during brachial artery infusions of acetylcholine (Ach), sodium nitroprusside (NTP), and angiotensin II (±nitric oxide synthase [NO]) synthase blockade with N G -monomethyl l -arginine [ l -NMMA]). On a separate day, baseline and insulin-regulated glucose ([3- 3 H]glucose) and FFA ([9,10- 3 H]palmitate) turnover were measured. The vasoconstrictor response to angiotensin II was greater ( P <0.05) in obese men than in nonobese men, whereas endothelium-dependent vasodilation was similar. The slope of the angiotensin II dose-response curve correlated significantly with the basal plasma palmitate concentration. Basal and insulin-mediated glucose disposal was significantly reduced and FFA turnover significantly increased in viscerally obese men. No differences in endothelium-independent vasodilation or relationships between vascular responsivity and palmitate and glucose kinetics or body composition were found. Angiotensin II–stimulated forearm vasoconstriction is increased in viscerally obese normotensive men.