Evolution of renal function and Na+, K+-ATPase expression during ischaemia-reperfusion injury in rat kidney

The aim of the present work was to study the effects of an unilateral ischaemic-reperfusion injury on Na+, K+-ATPase activity, α1 and β1 subunits protein and mRNA abundance and ATP content in cortical and medullary tissues from postischaemic and contralateral kidneys. Right renal artery was clamped for 40 min followed by 24 and 48 h of reperfusion. Postischaemic and contralateral renal function was studied cannulating the ureter of each kidney. Postischaemic kidneys after 24 (IR24) and 48 (IR48) hours of reperfusion presented a significant dysfunction. Na+, K+-ATPase α1 subunit abundance increased in IR24 and IR48 cortical tissue and β1 subunit decreased in IR48. In IR24 medullary tissue, α1 abundance increased and returned to control values in IR48 while β1 abundance was decreased in both periods. Forty minutes of ischaemia without reperfusion (I40) promoted an increment in α1 mRNA in cortex and medulla that normalised after 24 h of reperfusion. β1 mRNA was decreased in IR24 medullas. No changes were observed in contralateral kidneys. This work provides evidences that after an ischaemic insult α1 and β1 protein subunit abundance and mRNA levels are independently regulated. After ischaemic-reperfusion injury, cortical and medullary tissue showed a different pattern of response. Although ATP and Na+, K+-ATPase activity returned to control values, postischemic kidney showed an abnormal function after 48 h of reflow.