Endothelium-dependent inhibition of Na(+)-K+ ATPase activity in rabbit aorta by hyperglycemia. Possible role of...

Area of Science:

• Vascular Biology
• Endocrinology
• Biochemistry

Background:

• Hyperglycemia is known to impair vascular function.
• Sodium-potassium ATPase (Na(+)-K+ ATPase) plays a crucial role in maintaining vascular tone.
• Endothelium-derived nitric oxide (EDNO) is a key regulator of vascular relaxation.

Purpose of the Study:

• To investigate the impact of hyperglycemia on Na(+)-K+ ATPase activity in rabbit aorta.
• To elucidate the role of endothelium-derived nitric oxide (EDNO) in mediating the hyperglycemic effect on Na(+)-K+ ATPase.
• To explore the potential contribution of altered EDNO and Na(+)-K+ ATPase activity to vascular dysfunction in diabetes.

Main Methods:

• Rabbit aortic rings were incubated in varying glucose concentrations (5.5 mM or 44 mM).
• Na(+)-K+ ATPase activity was quantified using ouabain-sensitive 86Rb-uptake.
• Experiments involved manipulating the endothelium, using nitric oxide synthase inhibitors (NG-monomethyl L-arginine), and adding L-arginine or sodium nitroprusside.

Main Results:

• High glucose (44 mM) significantly decreased Na(+)-K+ ATPase activity (60%) in aortic rings with intact endothelium.
• Inhibition or removal of the endothelium mimicked the decrease in Na(+)-K+ ATPase activity observed under high glucose conditions.
• The hyperglycemic-induced decrease in Na(+)-K+ ATPase activity was reversed by L-arginine or sodium nitroprusside.
• Aortic Na(+)-K+ ATPase activity was also reduced in diabetic rabbits, particularly in the presence of endothelium.

Conclusions:

• Hyperglycemia-induced reduction in vascular Na(+)-K+ ATPase activity is partly mediated by decreased basal EDNO release.
• Impaired EDNO release and potentially altered Na(+)-K+ ATPase activity contribute to vascular relaxation deficits in hyperglycemia and diabetes.