Influence of sub-chronic diabetes mellitus on functional properties of renal Na(+),K(+)-ATPase in both genders of rats.

For characterization of Na+,K+-ATPase, a key enzyme involved in maintenance of intracellular sodium homeostasis, expression of alpha 1 subunit and the ATP- and Na+-binding properties were investigated by Western blot analysis and by enzyme kinetics, respectively. Previous studies documented time-dependent alteration of properties of renal Na+,K+-ATPase from its mobilization after 8 days to serious deteriorations after 16 weeks of diabetes in rats. Characterizing the critical period during development of the disease, when mobilization of Na+,K+-ATPase observed in the acute phase turns to its damage, we examined the enzyme properties after 8 weeks lasting diabetes which was induced by a single intraperitoneal administration of streptozotocin in a dose of 65 mg center dot kg(-1). The unchanged expression of Na+,K+-ATPase alpha 1-subunit in both genders indicates that 8 weeks represent the time when the mobilization of enzyme synthesis observed previously in acute diabetes is lost. In this time the renal Na+,K+-ATPase undergoes structural changes in the vicinity of Na+-binding site resulting in worsened affinity to sodium in both genders as indicated by 13% and 18% increase of K-Na value in female and male rats, respectively. However, gender specific was the diabetes-induced decrease in affinity to ATP by 18% which occurred in female rats only.