STUDIES ON THE MECHANISM OF EXERCISE PROTEINURIA

Abstract

In order to clarify the mechanism of exercise proteinuria, acute exercise for a short time and repeated exercise for long periods were loaded to 54 healthy adult students; and exercise proteinuria resulted was investigated, with reference to renal hemodynamics measured by clearance methods. The results obtained were as follows.
1) An average 1.01 (0.10-3.12)mg/min. of urinary protein excretion, accompanied with marked decrease in renal blood flow (-16.4--43.0%), glomerular filtration rate and K-and Na-clearance, was observed by loading an average 4300kgm of momentum, which was measured by ergometer. These effects of exercise on renal hemodynamics were observed to disappear in 80 minutes after exercise. Arterial O₂ saturation showed no significant changes during exercise, wheras arterial CO₂ content showed marked decrease.
2) Exercise proteinuria was observed to appear in most subjects by acute loading with over 3000kgm of momentum and urinary protein excretion was shown to increase in proportion to momentum of exercise.
3) The effects of exercise on renal function were observed to be generally more slight in trained subjects than in non-trained ones.
4) The effects of exercise on renal hemodynamic are similar to those of stimulation of sympathetic nervous system, and it is presumed that the effects of exercise observed here may be reffered to excitement of sympathetic nervous system during exercise.
5) During 7 to 17 days of repeated daily exercise, protein excretion up to 70.2mg/min. was observed to appear in early morning urine.
6) In rest periods, during 7 days of repeated daily exercise, proteinuria accompanying remarkable decrease in renal blood flow (-17.8--50.6%) was found to appear.
7) The appearance of proteinuria, accompanied with decrease in renal blood flow, in the early morning or in the rest after exercise during training term seems to be one of manifestations indicating accumulated fatique and to be an important sign in physical training.
8) In the above-mentioned experiments on exercise proteinuria, the glomerular permeability to protein was observed to increase during exercise, and close correlation was demonstrated between appearance of proteinuria and duration of decrease in renal blood flow. However, no correlation was found between exercise proteinuria and mean blood pressure or filtration fraction.
9) From the presented observations, it was presumed that the increased glomerular permeability to protein, due to the decreased renal blood flow caused by excitement of sympathetic nervous system, might play an important rôle in the pathogenetic mechanism of exercise proteinuria.