Enhanced renal tubular ouabain-sensitive ATPase in streptozotocin diabetes mellitus.

The effect of streptozotocin-induced diabetes mellitus on rat renal ouabain-sensitive ATPase in six distinct nephron segments was studied. Twenty-four hours after administration of streptozotocin, blood glucose increased threefold (P less than 0.001), and glucosuria was evident. Aldosterone levels increased almost twofold (P less than 0.001). Ouabain-sensitive ATPase increased in the proximal segments PC (proximal convoluted tubule) and PS (proximal straight tubule) by 43 and 62%, respectively, (P less than 0.001) and CD (cortical collecting duct) ouabain-sensitive ATPase increased 77% (P less than 0.001). Ouabain-sensitive ATPase in the cortical (CTAL) and medullary (MTAL) thick ascending limbs of Henle's loop and in the DC (distal convoluted tubule) remained unchanged after 24 h of streptozotocin administration. Eight days after streptozotocin administration, when glomerular filtration rate (GFR) was already markedly elevated, ouabain-sensitive ATPase remained increased in the PC, PS, and CD but was significantly less compared with the activity after 24 h (P less than 0.05), whereas in the CTAL and MTAL a marked increase in ouabain-sensitive ATPase occurred by 54% in the CTAL and 65% in the MTAL (P less than 0.001). Aldosterone levels remained elevated compared with control but less than after 24 h. Pretreatment with deoxycorticosterone acetate abolished the increase in ouabain-sensitive ATPase in the CD. These findings show that streptozotocin-induced diabetes mellitus in the rat is associated with a substantial increase in ouabain-sensitive ATPase activity along most of the nephron. This increase in enzyme activity may represent a mechanism of physiological adaptation of the nephron to maintain electrolyte homeostasis in diabetes in face of the increased GFR and osmotic diuresis.