Reduced Na-K pump but increased Na-K-2Cl cotransporter in aorta of streptozotocin-induced diabetic rat.
The activities of Na-K-ATPase and Na-K-2Cl cotransporter (NKCC1) were studied in the aorta, heart, and skeletal muscle of streptozotocin (STZ)-induced diabetic rats and control rats. In the aortic rings of STZ rats, the Na-K-ATPase-dependent (86)Rb/K uptake was reduced to 60.0 +/- 5.5% of the control value (P < 0.01). However, Na-K-ATPase activity in soleus skeletal muscle fibers of STZ rats and paired control rats was similar, showing that the reduction of Na-K-ATPase activity in aortas of STZ rats is tissue specific. To functionally distinguish the contributions of ouabain-resistant (alpha(1)) and ouabain-sensitive (alpha(2) and alpha(3)) isoforms to the Na-K-ATPase activity in aortic rings, we used either a high (10(-3) M) or a low (10(-5) M) ouabain concentration during (86)Rb/K uptake. We found that the reduction in total Na-K-ATPase activity resulted from a dramatic decrement in ouabain-sensitive mediated (86)Rb/K uptake (26.0 +/- 3.9% of control, P < 0.01). Western blot analysis of membrane fractions from aortas of STZ rats demonstrated a significant reduction in protein levels of alpha(1)- and alpha(2)-catalytic isoforms (alpha(1) = 71.3 +/- 9.8% of control values, P < 0.05; alpha(2) = 44.5 +/- 11.3% of control, P < 0.01). In contrast, aortic rings from the STZ rats demonstrated an increase in NKCC1 activity (172.5 +/- 9.5%, P < 0.01); however, in heart tissue no difference in NKCC1 activity was seen between control and diabetic animals. Transport studies of endothelium-denuded or intact aortic rings demonstrated that the endothelium stimulates both Na-K-ATPase and Na-K-2Cl dependent (86)Rb/K uptake. The endothelium-dependent stimulation of Na-K-ATPase and Na-K-2Cl was not hampered by diabetes. We conclude that abnormal vascular vessel tone and function, reported in STZ-induced diabetic rats, may be related to ion transport abnormalities caused by changes in Na-K-ATPase and Na-K-2Cl activities.
Michea
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L
National Institutes of Health, Bethesda, Maryland 20892-1603, USA.
Irribarra
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V
Goecke
I A
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Marusic
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ET
D000818:Animals; D001011:Aorta / Q000201:enzymology*; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D015153:Blotting, Western; D002034:Bumetanide / Q000494:pharmacology; D002352:Carrier Proteins / Q000378:metabolism*; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism*; D003925:Diabetic Angiopathies / Q000378:metabolism*; D004232:Diuretics / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000201:enzymology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006973:Hypertension / Q000378:metabolism; D066298:In Vitro Techniques; D007527:Isoenzymes / Q000032:analysis / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008297:Male; D009129:Muscle Tonus / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000502:physiology; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000493:pharmacokinetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D012414:Rubidium Radioisotopes; D028021:Sodium-Potassium-Chloride Symporters; D000254:Sodium-Potassium-Exchanging ATPase / Q000032:analysis / Q000037:antagonists & inhibitors / Q000378:metabolism*
D002352:Carrier Proteins; D004232:Diuretics; D004791:Enzyme Inhibitors; D007527:Isoenzymes; D012414:Rubidium Radioisotopes; D028021:Sodium-Potassium-Chloride Symporters; D002034:Bumetanide; D010042:Ouabain; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium