چكيده لاتين :
When the body is exposed to insults, the kidneys exhibit adaptive
changes termed renal cytoresistance, characterized by cholesterol
accumulation in the membranes of the tubule cells.
However, heavy muscle activity has not yet been accepted as
one of the stressors that could lead to cytoresistance. In order to
study the renal functional characteristics of animals exposed to
heavy muscle activity, rats were subjected to exhaustive treadmill
exercise for 5 days and their data was compared to those of
sedentary controls. It was found that in exercised rats, blood
lactate, muscle citrate synthase and proximal tubule peroxynitrite
levels were all elevated, suggesting the presence of oxidative
stress in the proximal tubule segments. However, mean
arterial pressure, renal blood flow, glomerular filtration rate,
fractional excretion of sodium and potassium, and organic anion
excretion remained normal. Despite unchanged blood cholesterol
levels, cholesterol loading in the proximal tubule segments,
especially the free form, and decreased lactate dehydrogenase
release from cytoresistant proximal tubule segments indicated
the development of renal cytoresistance. However, this resistance
did not seem to have protected the kidneys as expected
because organic anion accumulation associated with glycosuria
and proteinuria, in addition to the elevated urinary cholesterol
levels, all imply the presence of an impaired glomerular permeability
and reabsorption in the proximal tubule cells. Therefore,
we suggest that in response to heavy muscle activity the tubular
secretion may remain intact, although cytoresistance in the
proximal tubule cells may affect the tubular reabsorptive functions
and basolateral uptake of substances. Thus, this differential
sensitivity in the cytoresistance should be taken into account
during functional evaluation of the kidneys.
