Hyperglycemia increases endothelial superoxide that  impairs smooth muscle cell Na+-K+-ATPase activity

Nitric oxide (NO) plays an important role in the control of numerous vascular functions including basal Na+-K+-ATPase activity in arterial tissue. Hyperglycemia inhibits Na+-K+-ATPase activity in rabbit aorta, in part, through diminished bioactivity of NO. The precise mechanism(s) for such observations, however, are not yet clear. The purpose of this study was to examine the role of superoxide in modulating NO-mediated control of Na+-K+-ATPase in response to hyperglycemia. Rabbit aorta incubated with hyperglycemic glucose concentrations (44 mM) demonstrated a 50% reduction in Na+-K+-ATPase activity that was abrogated by superoxide dismutase. Hyperglycemia also produced a 50% increase in steady-state vascular superoxide measured by lucigenin-enhanced chemiluminescence that was closely associated with reduced Na+-K+-ATPase activity. Specifically, the hyperglycemia-induced increase in vascular superoxide was endothelium dependent, inhibited by l-arginine, and stimulated by N ω-nitro-l-arginine. Aldose reductase inhibition with zopolrestat also inhibited the hyperglycemia-induced increase in vascular superoxide. In each manipulation of vascular superoxide, a reciprocal change in Na+-K+-ATPase activity was observed. Finally, a commercially available preparation of Na+-K+-ATPase was inhibited by pyrogallol, a superoxide generator. These data suggest that hyperglycemia induces an increase in endothelial superoxide that inhibits the stimulatory effect of NO on vascular Na+-K+-ATPase activity.

Download Full-text

Role of endothelium-derived nitric oxide in stimulation of Na(+)-K(+)-ATPase activity by endothelin in rabbit aorta

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1994.266.2.h577 ◽

1994 ◽

Vol 266 (2) ◽

pp. H577-H582 ◽

Cited By ~ 6

Author(s):

S. Gupta ◽

C. McArthur ◽

C. Grady ◽

N. B. Ruderman

Keyword(s):

Nitric Oxide ◽

Smooth Muscle ◽

Atpase Activity ◽

Rabbit Aorta ◽

No Synthase ◽

Maximal Increase ◽

Synthase Inhibitor ◽

Cgmp Formation ◽

Stimulation Of

An endothelium-derived factor with the properties of nitric oxide (NO) has recently been implicated in the regulation of basal Na(+)-K(+)-adenosinetriphosphatase (ATPase) activity in vascular smooth muscle. To determine whether this factor also plays a role in the stimulation of ouabain-sensitive (OS) 86Rb uptake by specific agonists, studies were carried out using rabbit aortic rings. In endothelium-intact rings incubated for 3 h with Krebs-Henseleit solution containing 5.5 mM glucose, endothelin (ET) caused a concentration-dependent increase in OS 86Rb uptake (maximal increase = 205%, with 100 nM ET). Incubation with phenylephrine (Phe; 0.1 and 1 microM) or phorbol 12,13-dibutyrate (PDBu; 0.1 microM), under the same conditions, increased OS 86Rb uptake by 128, 144, and 140%, respectively. Removal of endothelium before incubation decreased the ability of ET to stimulate OS 86Rb uptake by 38–45%, but it did not diminish the stimulation of OS 86Rb uptake by Phe or PDBu. An increase in the concentration of glucose from 5.5 to 44 mM diminished ET-stimulated OS 86Rb uptake by 50% in endothelium-intact rings but had no effect on Phe- or PDBu-induced increases in OS 86Rb uptake. Addition of the NO synthase inhibitor NG-monomethyl-L-arginine (L-NMMA; 0.3 mM) to the medium decreased ET-stimulated OS 86Rb uptake by 40%. Guanosine 3',5'-cyclic monophophate (cGMP) formation in endothelium-intact rings was also increased (65%) by ET but not by Phe or PDBu. The increase in cGMP by ET was totally inhibited by L-NMMA or endothelium denudation.(ABSTRACT TRUNCATED AT 250 WORDS)

Download Full-text

Role of an aprotinin-sensitive protease in the activation of Ca2+-ATPase by superoxide radical (O2-.) in microsomes of pulmonary vascular smooth muscle

Biochemical Journal ◽

10.1042/bj3170885 ◽

1996 ◽

Vol 317 (3) ◽

pp. 885-890 ◽

Cited By ~ 29

Author(s):

Tapati CHAKRABORTI ◽

Salil K. GHOSH ◽

John R. MICHAEL ◽

Sajal CHAKRABORTI

Keyword(s):

Superoxide Dismutase ◽

Smooth Muscle ◽

Vascular Smooth Muscle ◽

Atpase Activity ◽

Molecular Mass ◽

Protease Activity ◽

Superoxide Radical ◽

Polyclonal Antiserum ◽

Generating System

We have investigated the role of an aprotinin-sensitive protease in regulating Ca2+-ATPase activity and Ca2+ uptake (ATP-dependent and Na+-dependent) in microsomes of bovine pulmonary vascular smooth muscle during treatment with the O2-•-generating system hypoxanthine plus xanthine oxidase. Treatment of the smooth muscle microsomes with the O2-•-generating system produced a protease in a gelatin-containing zymogram with an apparent molecular mass of 16 kDa. This 16 kDa proteolytic protein was found to be inhibited by superoxide dismutase (SOD) and aprotinin but not by PMSF. Using polyclonal antiserum to aprotinin, we found that it is an ambient antiprotease of the smooth muscle microsomes. Treatment of the microsomes with the O2-•-generating system stimulated protease activity tested with a synthetic substrate N-benzoyl-dl-arginine p-nitroanilide and also enhanced Ca2+-ATPase activity. It also stimulated ATP-dependent Ca2+ uptake. In contrast, Na+-dependent Ca2+ uptake was found to be inhibited by the O2-•-generating system. Pretreatment of the microsomes with SOD and aprotinin preserved the increase in protease activity, Ca2+-ATPase activity and ATP-dependent Ca2+ uptake. In addition, O2-•-caused inhibition of the Na+-dependent Ca2+ uptake which was reversed by SOD and aprotinin. Pretreatment with PMSF did not cause any discernible alteration in the protease activity, Ca2+-ATPase activity, ATP-dependent Ca2+ uptake and Na+-dependent Ca2+ uptake in the microsomes caused by the O2-•-generating system. These results suggest that an aprotinin-sensitive protease plays a pivotal role in regulating Ca2+-ATPase and Ca2+-uptake activities in microsomes of pulmonary vascular smooth muscle under oxidant O2-•-triggered conditions.

Download Full-text