Abstract
The relationship between the diastolic arterial pressure and blood volume or plasma volume (pressure-volume relationship) and that between plasma volume and endogenous creatinine clearance (Ccr) were investigated in chronic glomerulonephritis patients. Patients were divided into two groups, normotensive and hypertensive. In the normotensives (diastolic pressure_??_80 mmHg, Ccr=90±5 ml/min), the diastolic pressure correlated negatively with blood volume and plasma volume. In the hypertensives (diastolic pressure>80 mmHg, Ccr=66±9ml/min), the diastolic pressure positively correlated with blood volume and plasma volume. In the normotensives, there was a positive correlation between plasma volume (ml) (PV) and Ccr; the relation was: Ccr=0.068 PV0.91....(l). On the other hand, in the hypertensives, PV tended to increase with a decrease in Ccr, but there was no significant correlation between the two. If glomerular filtration rate (GFR) is a function of PV, as can be presumed from the relation shown in equation (1), and pressure diuresis is caused mainly by a decrease in tubular reabsorption with an increase in peritubular capillary pressure, urine volume (V), as a function of arterial pressure (AP) and that of PV, can be expressed as: V=f1(AP)f2(PV), where df1/dAP and df2/dPV are positive. Using this relation in the stationary state of body fluid volume (V=constant), the turn of pressurevolume relationship from negative to positive in chronic glomerulonephritis patients seems to be caused by the transform of f2 in the normal range of arterial pressure into f3 (df3/dPV<0, a new PV-GFR relation) in the higher range of arterial pressure, provided that df1/dAP is positive in both normotensive and hypertensive patients.
