Whole-body 201Tl scintigraphy during one-leg exercise and at rest in normal subjects: estimation of regional blood flow changes.

To determine the effect of exercise intensity on regional blood flow in exercising and resting leg muscles and organs, we assessed relative changes in the regional distribution of 201Tl during one-leg ergometer exercise and at rest by whole-body scintigraphy as an estimate of regional blood flow changes in 10 healthy males. The regional 201Tl activity was expressed as a percentage of the whole-body activity, and relative changes in each region were compared to those at the anaerobic threshold (AT) and at peak exercise. In the legs, the distribution of 201Tl in the exercising thigh and calf increased significantly at the AT to 390.7 and 219.2% respectively of resting levels (both P < 0.01), but remained unchanged the resting thigh from rest to peak exercise. Conversely its distribution in the resting calf decreased significantly at the AT to 60.0% of the resting level (P < 0.01). However, there were no significant differences between AT and peak exercise. In the organs, the distribution of 201Tl in the lung, liver, spleen and kidneys decreased significantly at the AT to 88.4 +/- 10.4%, 67.0 +/- 11.5%, 62.4 +/- 11.8% and 67.0 +/- 8.6% respectively of resting levels (all P < 0.01). Redistribution of blood flow to the exercising leg occurs predominantly during mild to moderate exercise. Therefore, blood flow in the leg during strenuous exercise depends primarily upon an increase in cardiac output. The splanchnic organs are the major sources of redistribution.