The relationships of circulating plasma volume (
PV) to effective renal plasma flow and glomerular filtration rate (
GFR) were investigated in reference to their interrelated changes induced by upright posture in normal subjects and patients with chronic glomerulonephritis. The following relation was obtained: (percentage change in
GFR) =
k(percentage change in
PV). The values of
k were 3.4 for the normal and 3.1 for the patients. There was no statistically significant difference between the two. On account of the above relation the recumbent level of glomerular filtration rate (
GFR)
r was derived from the recumbent level of circulating plasma volume (
PV)
r as follows: (
GFR)
r=
Kp [(
PV)
r]
k, where
Kp is a constant. On the other hand, the decreases (percentage) in effective renal plasma flow were biphasically related to those in
PV. Mean arterial pressure rose in upright posture in many cases, but its changes (percentage) showed no correlation with the changes (percentage) in
GFR. These results suggest that in a small decrease in
PV, GFR does not decrease with the fall in mean arterial pressure, but with the power function of
PV. The possible mechanisms of these changes in renal function are examined with special reference to the structure of renal arterial system.
View full abstract