Electrolyte handling in the isolated perfused rat kidney: demonstration of vasopressin V2-receptor-dependent calcium reabsorption

Figures & data

Figure 1. Perfusion, glomerular filtration rate (GFR), and diuresis in kidneys perfused with 6% or 7.5% bovine serum albumin (BSA), respectively. *p < 0.05 between groups, repeated measures ANOVA.

Table 1. Three-hour mean values in kidneys perfused with 6% or 7.5% bovine serum albumin (BSA) or 7.5% BSA + desmopressin (DDAVP; 400 ng/L).

	6% BSA	7.5% BSA	7.5% BSA + DDAVP
Perfusion (mL/min)	58 ± 3	60 ± 4	54 ± 2
GFR (μL/min)	899 ± 105	684 ± 90	747 ± 96
Urine flow (μL/min)	167 ± 30	61 ± 14^a	27.67 ± 7.96
FRNa	0.88 ± 0.02	0.96 ± 0.01^a	0.97 ± 0.01
FRK	0.38 ± 0.02	0.51 ± 0.02^a	0.61 ± 0.03^b
Urine Na/K ratio	10.33 ± 1.63	3.61 ± 0.74^a	3.34 ± 1.07
FRCl	0.86 ± 0.02	0.95 ± 0.01^a	0.97 ± 0.01
FRCa	0.79 ± 0.02	0.92 ± 0.01^a	0.99 ± 0.00^b
FR glucose	0.96 ± 0.01	0.97 ± 0.00^a	0.98 ± 0.00
Urine osmolality (mOsm/kg)	241 ± 9	230 ± 9	353 ± 9^b

^a p < 0.05 versus 6% BSA.

^b p < 0.05 versus 7.5% BSA.

Ca: calcium; Cl: chloride; FR: fractional reabsorption; GFR: glomerular filtration rate; K: potassium; Na: sodium.

Figure 2. Urine osmolality, fractional calcium (FR_Ca), and sodium reabsorption (FR_Na) in kidneys perfused with desmopressin (DDAVP; 400 ng/L) compared to control experiments. The bars represent mean values from the period 90–180 min (indicated by the line). Albumin concentration in the perfusate was 7.5%. *p < 0.05 versus control.

Figure 3. Correlation between change (Δ) in urine osmolality (A) and urine flow (B) and fractional calcium reabsorption (FR_Ca) in kidneys perfused with 7.5% albumin without DDAVP. Values are calculated as the change from the first 10-min period up to 60 min into the experiment. The values are individual time points derived from the two experimental groups without added DDAVP. A straight line was fitted to the data using linear regression, with the square of the correlation coefficient (R²) indicated.

Figure 4. Fractional reabsorption of sodium (FR_Na) and potassium (FR_K) in response to amiloride (5 µmol/L) in kidneys perfused with BSA 7.5% or BSA 7.5% + desmopressin (DDAVP; 400 ng/L). The left panel presents the time series data of fractions observed during the 120-min experiment period, whereas the right panel displays mean values at baseline (0–60 min) and at amiloride exposure (60–120 min). *p < 0.05 versus baseline.