The nephrotoxicity risk in rats subjected to heavy muscle activity

When the body is exposed to insults, the kidneys exhibit adaptivechanges termed renal cytoresistance, characterized by cholesterolaccumulation in the membranes of the tubule cells.however, heavy muscle activity has not yet been accepted asone of the stressors that could lead to cytoresistance. in order tostudy the renal functional characteristics of animals exposed toheavy muscle activity, rats were subjected to exhaustive treadmillexercise for 5 days and their data was compared to those ofsedentary controls. it was found that in exercised rats, bloodlactate, muscle citrate synthase and proximal tubule peroxynitritelevels were all elevated, suggesting the presence of oxidativestress in the proximal tubule segments. however, meanarterial pressure, renal blood flow, glomerular filtration rate,fractional excretion of sodium and potassium, and organic anionexcretion remained normal. despite unchanged blood cholesterollevels, cholesterol loading in the proximal tubule segments,especially the free form, and decreased lactate dehydrogenaserelease from cytoresistant proximal tubule segments indicatedthe development of renal cytoresistance. however, this resistancedid not seem to have protected the kidneys as expectedbecause organic anion accumulation associated with glycosuriaand proteinuria, in addition to the elevated urinary cholesterollevels, all imply the presence of an impaired glomerular permeabilityand reabsorption in the proximal tubule cells. therefore,we suggest that in response to heavy muscle activity the tubularsecretion may remain intact, although cytoresistance in theproximal tubule cells may affect the tubular reabsorptive functionsand basolateral uptake of substances. thus, this differentialsensitivity in the cytoresistance should be taken into accountduring functional evaluation of the kidneys.