Summary
Altogether 33 Finnish amateur runners were studied before and after a non-competitive
Marathon run over the classical itinerary in Athens in 1976 (n = 8), 1977 (n = 14)
and 1978 (n = 11). Plasma renin activity (PRA) rose 3-fold in all runs, whereas plasma
renin substrate (RS) concentration did not change significantly. Serum angiotensin
converting enzyme (ACE) activity was not changed. Serum cortisol concentration was
increased 2-3 fold. The unchanged plasma RS concentration, in spite of increasing
PRA, indicates that plasma RS is kept within normal limits during prolonged strenuous
physical exercise. One contributing mechanism may be stimulation of RS biosynthesis
by cortisol. Low PRA levels in two old runners, 65 and 83 years old, may indicate
a decreased ability to respond with renin release to the stimuli of physical exercise.
Key-Words:
Marathon Run
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Strenuous Exercise
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Renin
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Renin Substrate
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Angiotensin Converting Enzyme
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Cortisol
