ISSN:
1432-0428
Keywords:
Na+-K+-ATPase
;
insulin
;
vascular smooth muscle
;
vasodilation
;
vasoconstriction
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary To determine whether insulin regulates vascular smooth muscle Na+, K+-ATPase activity and if impaired insulin stimulation of vascular smooth muscle Na+, K+-ATPase activity could be a cause of increased vascular reactivity to norepinephrine and angiotensin II in diabetic states, the effects of insulin on Na+, K+-ATPase activity were examined in normal rabbit aortic intima-media incubated with normal plasma glucose and myo-inositol levels for 30 min. Insulin at 100 μU/ml (600 pmol/l) had no effect on Na+, K+-ATPase activity. At 250 μU/ml it caused a 4.2±0.8% increase, and at 500 μU/ml insulin caused a 17.7±1.4% increase in Na+, K+-ATPase activity that was completely inhibited by amiloride (1 mmol/l). Human insulin-like growth factor I (600 pmol/l) caused an 18.0±1.0% increase in Na+, K+-ATPase activity that was inhibited by amiloride. Insulin does not regulate (stimulate) aortic vascular smooth muscle Na+, K+-ATPase activity. Supraphysiological insulin concentrations, probably acting through an insulin-like growth factor I receptor, stimulate Na+/H+ exchange in aortic vascular smooth muscle and cause small secondary increases in Na+, K+-ATPase activity. In aortic intima-media incubated with normal plasma glucose and myo-inositol levels, endogenously released adenosine stimulates and maintains a component of resting Na+, K+-ATPase activity and stimulates acute increases in activity when norepinephrine (1 μmol/l) or angiotensin II (100 nmol/l) is added. These adenosine-stimulated components of Na+, K+-ATPase activity are selectively inhibited when the medium glucose is raised to 30 mmol/l during a 30-min equilibration and 30-min incubation. Insulin (100 μU/ml) added during the incubation had no effect on the alterations in Na+, K+-ATPase activity induced by glucose at an elevated plasma level. Impaired insulin stimulation of vascular smooth muscle Na+, K+-ATPase activity is not a possible cause for alterations in vascular reactivity in diabetes.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00399952
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