THE RENAL CIRCULATION 1 495 



300 -- 



ZOO mmHg 300 



fig. 28. Immediate and stabilized relationship of renal 

 blood flow to perfusion pressure. [After Thurau & Kramer 

 (308).] 



¥,0 



3,0 



10 



10 











eo 



¥0 



so 



so 



700 



720 



7W 



fig. 29. Immediate and stabilized response of renal blood 

 flow to decrease in perfusion pressure. O: Immediate flow; •: 

 stabilized flow; X : immediate response to restoration of pressure, 

 then return to control ( •) cluster, at upper end of curve. The 

 numbers indicate sequence of response. [After Grupp et 

 al. (120).] 



of the vascular smooth muscle; when low, overshoot 

 was greater than when tonus was high. The capillary 

 volume increases transiently during the phase of 

 overshooting (increase is with downward deflection of 

 the galvanometer) accompanying the initial passive 

 expansion of arteries and arterioles as pressure is 

 suddenly increased. Then, as total flow settles to 



BLOOD PRESSURE 



BLOOD FLOW 



GALV. 

 DEFLECTION 



WEIGHT 



120 



fig. 30. Immediate and delayed adjustment to rectilinear 

 increase in blood pressure — renal blood How, superficial corti- 

 cal blood volume (galvanometer deflection) — and kidney 

 weight. (Downward deflection of galvanometer indicates in- 

 crease in volume.) Weight change is an approximation of trend. 

 [After Thurau & Kramer (307).] 



lower levels after the onset of the myogenic contrac- 

 tion, capillary content decreases somewhat. 



Upon decrement of pressure, flow decreases mark- 

 edly below the control, indicative of the contracted 

 state of the resistance vessels. Then normal flow is 

 slowly restored as the myogenic response recedes. 

 Capillary blood content during this decrement in 

 flow also decreases significantly, then is restored as 

 total flow rises. 



The weight change may show a triphasic response 

 in experiments with more prolonged stages: a) an 

 initial rapid increment as blood surges into the re- 

 laxed vessels; b) a transient drop as the myogenic re- 

 sponse occurs; and c) a secondary rise. The last may 

 be the result of increased transudation of fluid through 

 the capillaries at the elevated pressure and increased 

 flow. 



The dynamic reactivity implied in these fairly- 

 rapid adjustments corresponds to the type of reac- 



