THE RENAL CIRCULATION 



I 50I 



80 



sec 

 60- 



W 



20 



fig. 34. Mean transit time during 

 diuresis and antidiuresis as a function of 

 CHoO (water concentration); T§ 20 : os- 

 motic water deficit, i.e., below equilib- 

 rium point. [After Thurau et al. (309).] 



the loop of Henle in the countercurrent system is indi- 

 cated, and this becomes the modern role of the former 

 Trueta juxtamedullary shunt. 



RESPONSE OF RENAL BLOOD FLOW 

 TO PHYSIOLOGICAL STRESS 



The dog and man differ significantly in the response 

 of the renal blood flow to exercise. The canine kidney- 

 shows a considerable amount of autonomy of circula- 

 tion during exercise to a degree which results in sig- 

 nificant reduction in blood flow in man. Blake (23) 

 exercised dogs on a treadmill at the rate of 2.5 mph 

 for 40 min and observed no significant changes in 

 Cpah and C'cr- In one of three dogs tested, when "emo- 

 tional" stimulus was superimposed (a loud horn), 

 Cpah decreased from 161 to 137 ml per min, then re- 

 turned. C Cr did not change. Greater effects were noted 

 on sodium excretion, which decreased during the 

 emotional response. Carlin et al. (50) ran their dogs 

 at 5.6 to io mph on a 15 grade for 7 to 20 min; pulse 

 rate was often over 160 per min, and respiratory 

 rate, over 300 per min. Yet there was no change in 

 Cpah or C In , and sodium excretion did not change sig- 

 nificantly. 



Recumbent human subjects pedaling the equiva- 

 lent of 0.5 kg weight at 60 cycles per min, which 

 doubled their resting oxygen consumption, showed a 

 20 per cent reduction in RPF, while GFR remained 

 unchanged, as did £ PAH (42). Sodium excretion de- 

 creased by 20 per cent. Chapman et al. (52) worked 

 their normal male subjects on a treadmill for 16-min 

 periods. The following decreases in C PAH were noted : 

 at 3.0 mph at o grade, 6 per cent; 3.0 mph at 5 per 

 cent grade, 17 per cent; at 3.5 mph at 10 per cent 

 grade, 25 per cent below resting control. Work was 



continued for another 16-min period, with the follow 

 ing decreases: 15, 27, and 35 per cent, respectively. 

 Recovery was incomplete after 40 min. In a subse- 

 quent study (53), the above results were confirmed 

 and, in addition, the work period (3 mph at j'~, 

 grade) was prolonged to 3 hours; during the second 

 and third hours, C PA h decreased no more than it had 

 during the first hour ( — 18.510 —33.7 % below control). 

 Recovery occurred in about an hour. Radigan & 

 Robinson (250) observed that exercise (3 mph on a 5 ' . 

 grade) produced a 42 per cent decrease in RPF, but 

 the C ln did not change when the environmental tem- 

 perature was cool (21 C); when the work was done 

 in a hot environment (50 C), C' In decreased by 16.5 

 per cent, with a 36 per cent decrease in C PAH . In 

 another study, subjects who had run the 440-yard 

 dash at full speed had reductions of 18 to 54 per cent 

 below control in C D , and exhibited also decrease in 

 C In (10). The apparent blood flow remained reduced 

 for 10 to 40 min postexercise. 



Harpuder et al. (134) compared different grades of 

 work in different postures on C PAH . Light work (3500 

 kg-m) in the erect or sitting position had no significant 

 effect. At ca. 4800 kg-m, C PAH decreased to 0.85 ± 

 .08 of control in the supine, as compared to 0.69 ± .04 

 in the erect position. At 9120 kg-m in the erect posture, 

 the reduction was 0.55 ± .10. At the peak of exer- 

 cise, blood pressure had risen from 1 14/72 to 164/82 

 mm Hg, and heart rate from 64 to 1 42 per min. They 

 point out that with a normal renal blood flow about 

 1 liter per min (2o'<' of the cardiac output), a saving 

 of 0.5 liter per min is made available for the circula- 

 tion of active tissues. White & Rolf (339) similarly- 

 analyzed the effects of running exercise With brief 

 maximum exercise, RPF decreased to 20 per cent of 

 control, and under extreme conditions they predicted 

 that almost 1 liter per min of blood was made available 

 or the active tissues. 



The cardiac patient shows more marked renal re- 



