Effects of streptozotocin-induced diabetes on glomerular filtration rate and renal Na+-K+-ATPase activity in mice

Glomerular filtration rate (GFR) and microsomal Na+-K+-ATPase activity in the renal cortex and medulla of mice with streptozotocin-induced diabetes mellitus were studied over a period of 100 days (3, 18, 50 to 100 days). GFR increased by 44, 218, 358 and 402%, respectively and renal hypertrophy (17, 21, 45, and 56% increase) was observed at these four different time courses, respectively. Na+-K+-ATPase activity in the diabetic cortex increased by 28, 40, 50 and 69%, respectively, while that in the medulla increased by 21, 45, 58 and 57%, respectively. On the other hand, Mg2+-ATPase activity failed to increase until 50 days after the onset of diabetes in both the cortex and medulla. The alterations in ATPase activity were specific, while for 5'-nucleotidase activity was not changed. The increase in Na+-K+-ATPase activity in the cortex and medulla closely paralleled the increase in GFR and renal hypertrophy over the experimental period from 3 to 100 days. Therefore, from early to long term diabetes, the renal hypertrophy and increased GFR were associated with the increased Na+-K+-ATPase activity in renal tubules.