Cortical Na+,K+-ATPase activity, abundance and distribution after in vivo renal ischemia without reperfusion in rats

The aim of our work was to study the changes in activity, abundance and dis tribution of sodium, potassium-adenosine triphosphatase (Na+,K+-ATPase) in membranes of cortical tubular cells in an in vivo model of ischemic injury without reperfusion. Na+,K+-ATPase, alkaline phosphatase (AP) activities an d their distribution in membranes isolated from renal cortex using a Percol l gradient were studied after different ischemic periods. Na+,K+-ATPase a-s ubunit protein abundance was analysed by Western-blot. Plasma urea and cort ical adenosine 5'triphosphate (ATP) were also measured. In cortical homogen ates 5 min of ischemia promoted a diminution in ATP content. Na+,K+-ATPase activity diminished after 40 min and AP after 100 min of ischemia. Na+,K+-A TPase activity in the Percoll gradient fractions after 5 min peaked at a hi gher density and was significantly decreased after 40 min. AP activity was decreased in typically enriched apical membranes after both times of ischem ia. At each time studied Na+,K+-ATPase abundance was increased in cortical homogenates and membranes. Our results showed opposite effects of ischemia on Na+,K+-ATPase activity and abundance. Increased levels of Na+,K+-ATPase protein were observed. The enzyme would be rapidly delivered to membrane do mains and become inactivated as ischemia persists. Copyright (C) 2001 S. Ka rger AG, Basel.