Prospective validation of single plasma sample 99mTc-ethylenedicysteine clearance in adults.
99mTc-L,L-ethylene, L, dicysteine (EC) clearance shows strong correlation with orthoiodohippurate clearance, and it is possible to estimate effective renal plasma flow from 99mTc-EC clearance. In routine clinical studies, it is practical to use the one or two plasma sample method instead of multiple plasma samples for clearance determination. A single-sample technique was developed for 99mTc-EC, and a regression formula was generated. A prospective study tested the validity of this regression formula. METHODS: The study population was composed of 26 patients with a wide range of renal function. Multiple plasma sample 99mTc-EC clearances were calculated from all patients using the open two-compartment model. Single plasma sample clearances were also determined from the 54-min plasma sample using the regression formula published previously. RESULTS: The multiple-sample plasma clearance of 99mTc-EC ranged from 46 to 668 mL/min with a mean of 300.76 +/- 150.73 mL/min. The clearances obtained from the 54-min plasma sample ranged from 49 to 699 mL/min, with a mean of 297.39 +/- 152.23 mL/min. There was an excellent correlation between the clearances obtained by the two techniques (r = 0.99, slope = 0.9911). The standard error of estimation was found to be 25.9 mL/min. CONCLUSION: This study suggests that 99mTc-EC clearance can be estimated from 54-min plasma samples with an acceptable error of estimation for most routine clinical studies. (+info)
Augmentation of diabetes-associated renal hyperfiltration and nitric oxide production by pregnancy in rats.
We tested the hypothesis that pregnancy might increase diabetes-associated nitric oxide (NO) production and renal hyperfiltration. Two weeks following i.v. streptozotocin (40 mg/kg), mean arterial pressure (MAP) was not modified by diabetes; glomerular filtration rate (GFR), renal plasma flow (RPF) and filtration fraction (FF) were higher in pregnant than in virgin controls and increased by diabetes to a greater extent in pregnant than in virgin rats. Urinary volume (UV), creatinine, albumin and sodium (UNaV) were significantly increased by diabetes. Diabetes led to an increase in renal, cardiac, aortic and uterine but not in placental NO synthase activities. Infusion of NG-nitro-l-arginine (l-NA) caused a dose-dependent reduction in GFR, RPF, plasma NO2-/NO3-, UV and UNaV; in general, diabetes increased these effects to a greater extent in pregnant than in virgin rats. l-NA increased MAP in all groups of rats but did not alter FF. Diabetes did not alter responses of thoracic aorta rings to vasoconstrictor effects of phenylephrine and the vasorelaxant effects of sodium nitroprusside but increased endothelium-dependent relaxant effects of acetylcholine. In general the effects of diabetes of 7 days duration were similar to those described above for diabetes of 14 days duration. These data suggest that diabetes-associated renal hyperfiltration and NO production are augmented by pregnancy. (+info)
Dynamic SPECT evaluation of renal plasma flow using technetium-99m MAG3 in kidney transplant patients.
OBJECTIVE: The purpose of this study was to evaluate Patlak's graphic analysis method to determine renal plasma flow (RPF) in kidney transplants. METHODS: Dynamic SPECT was performed with 99mTc MAG3 in 12 patients. RPF was determined by both Patlak's graphic analysis method and Russell's method. Ventral, central and dorsal tomographic images of the transplanted kidney were reconstructed to estimate intrarenal distribution of renal plasma flow. RESULTS: The renal influx constant (Ku) calculated by Patlak's graphic analysis method was reproducible and correlated with both serum creatinine (r = -0.88, P < 0.001) and blood urea nitorogen levels (r = -0.82, P < 0.002). However, a significant difference was noted between the RPF values derived from Patlak's graphic analysis method and Russell's method. Ku was corrected by a factor calculated from raw and reconstructed data, and the resulting values were in fair agreement with those determined by Russell's method. CONCLUSION: These methods are useful in evaluating the function of transplanted kidneys. (+info)
The dynamics of glomerular filtration after Caesarean section.
The objective of this study was to determine whether the glomerular hyperfiltration of pregnancy is maintained even after Caesarean section and, if so, to define the responsible hemodynamics. The dynamics of glomerular filtration were evaluated in 12 healthy women who had just completed an uncomplicated pregnancy and were delivered by Caesarean section. Age-matched but non-gravid female volunteers (n = 22) served as control subjects. GFR in postpartum women was elevated above control values by 41%; 149+/-10 versus 106+/-3 ml/min per 1.73 m2, respectively (P < 0.001). In contrast, corresponding renal plasma flow was the same in the two groups, such that the postpartum filtration fraction was significantly elevated by 20%. Computation of glomerular intracapillary oncotic pressure (piGC) from knowledge of plasma oncotic pressure and the filtration fraction revealed this quantity to be significantly reduced in postpartum women, 20.6+/-1.7 versus 26.1+/-2.0 mmHg in control subjects (P < 0.001). A theoretical analysis of glomerular ultrafiltration suggests that depression of piGC, the force opposing the formation of filtrate, is predominantly or uniquely responsible for the observed postpartum hyperfiltration. (+info)
Renal function in mice: effects of volume expansion and angiotensin II.
The present study was performed to validate a simple means for assessing renal function in anesthetized mice and to characterize the renal hemodynamic responses to acute volume expansion and how these responses are altered by concurrent angiotensin II (AngII) infusions. Inulin and para-aminohippurate clearances were used to assess GFR and renal plasma flow (RPF) in three groups of male C57Bl/6 mice anesthetized with inactin (100 mg/kg, intraperitoneally) and ketamine (10 mg/kg). To avoid the hypotension associated with repeated blood sampling, a single blood sample was taken after three timed urine collections. Renal function and mean arterial pressure (MAP) were measured under euvolemic conditions (2.5 microl/min, intravenously, n = 7) during isotonic saline volume expansion (12.5 microl/min, intravenously, n = 5) and during volume expansion with concurrent AngII infusion (5 ng/min x g, n = 5). MAP in the control group was 77 +/- 2 mmHg; volume expansion alone did not change MAP significantly (83 +/- 2 mmHg), but led to significantly greater values in both GFR and RPF (1.35 +/- 0.14 versus 1.01 +/- 0.1 ml/min x g and 11.26 +/- 1.39 versus 6.29 +/- 0.5 ml/min x g, respectively). Infusion of AngII during volume expansion led to significant elevations of MAP (100 +/- 3 mmHg, P < 0.05) and prevented the increases in GFR and RPF elicited by volume expansion (0.77 +/- 0.08 and 5.35 +/- 0.48 ml/min x g, respectively). Volume expansion also elicited marked increases in absolute and fractional sodium excretion (6.1 +/- 1.0 versus 0.62 +/- 0.2 microEq/min x g and 3.1 +/- 0.7 versus 0.4 +/- 0.1%, respectively). AngII infusion attenuated the absolute and fractional sodium excretion responses to volume expansion (3.4 +/- 1.2 microEq/min x g and 2.5 +/- 0.5%, respectively). The present findings demonstrate that anesthetized mice exhibit marked renal hemodynamic and excretory responses to isotonic saline volume expansion. Concomitant AngII infusion attenuates these responses in spite of greater increases in arterial pressure. (+info)
Examination of the pathogenesis of diabetic nephropathy in OLETF rats.
We conducted protein loading to examine the progression and pathogenesis of diabetic nephropathy. For this experiment, male OLETF, LETO, F344 and BN rats were used. This experiment was performed on rats between 5 and 30 weeks of age. Examination parameters included body weight, food intake, oral glucose tolerance test (OGTT), urinary protein level (UP), urinary albumin level (UA), glomerular filtration rate (GFR), kidney weights, light microscopy (LM) and electron microscopy (EM). In the protein-loaded OLETF group, the UP level was markedly increased 20 weeks or more after birth. In OLETF control group, GFR were higher than those in other strains. Glomerular hypertrophy and kidney weights were markedly increased in protein-loaded groups in OLETF rats. Thirty weeks after birth, EM showed that the number of polyethyleneimine (PEI) of the glomerular basement membrane (GBM) in protein-loaded OLETF group was significantly decreased compared to that in control group. These changes in OLETF rats were more marked in the protein-loaded group than those in the control group. LM showed that the number of exudative lesions with fibrin-cap in the protein-loaded OLETF group was significantly increased than those in control group. In OLETF rats, protein loading caused deterioration of nephropathy at 30 weeks of age. Therefore, it was demonstrated that not only blood sugar control but also protein intake factors play important roles in the deterioration of nephropathy in OLETF rats. (+info)
Sodium handling in patients with well compensated cirrhosis is dependent on the severity of liver disease and portal pressure.
BACKGROUND AND AIMS: To test the contribution of portal pressure gradient (PPG) and neurohumoral factors to sodium handling in cirrhotic patients without ascites, by comparing preascitic cirrhotic patients with patients with transjugular intrahepatic portosystemic stent shunt (TIPSS) and previous ascites. PATIENTS: Ten patients with TIPSS and 10 preascitic cirrhotic patients. METHODS: Changes in glomerular filtration, renal plasma flow, urinary sodium excretion (U(Na)V), and neurohumoral factors were measured before and for two hours after infusion of one litre of 0. 9% saline over one hour. RESULTS: Glomerular filtration rate and renal plasma flow were significantly higher in patients with TIPSS compared with preascitic cirrhotic patients. Following saline infusion both parameters increased significantly; this increase was significantly greater in patients with TIPSS. U(Na)V increased significantly in both groups following saline infusion. The increase in U(Na)V was significantly greater in the TIPSS group. Plasma renin activity and angiotensin II decreased significantly in both groups. Basal U(Na)V was independently correlated with angiotensin II concentration and PPG and the change in U(Na)V correlated with the PPG. CONCLUSIONS: Results suggest that patients with advanced liver disease and low portal pressure handle sodium as well as patients with compensated liver disease and high portal pressure. These results are consistent with the notion that in addition to peripheral vasodilatation and severity of liver disease, the severity of portal hypertension contributes to the abnormalities of sodium retention in cirrhosis. (+info)
Glomerular hemodynamics in severe obesity.
Differential solute clearances were used to characterize glomerular function in 12 nondiabetic subjects with severe obesity (body mass index >38). Nine healthy subjects served as the control group. In the obese group, glomerular filtration rate (GFR) and renal plasma flow (RPF) exceeded the control value by 51 and 31%, respectively. Consequently, filtration fraction increased. The augmented RPF suggested a state of renal vasodilatation involving, mainly or solely, the afferent arteriole. Albumin excretion rate and fractional albumin clearance increased by 89 and 78%, respectively. Oral glucose tolerance tests were suggestive of insulin resistance. Insulin resistance was positively correlated with GFR (r = 0.88, P<0.001) and RPF (r = 0.72, P <0.001). Mean arterial pressure was higher than in the control group. Fractional clearances of dextrans of broad size distribution tended to be lowered. The determinants of the GFR were estimated qualitatively by using a theoretical model of dextran transport through a heteroporous membrane. This analysis suggests that the high GFR in very obese subjects may be the result of an increase in transcapillary hydraulic pressure difference (DeltaP). An abnormal transmission of increased arterial pressure to the glomerular capillaries through a dilated afferent arteriole could account for the augmentation in DeltaP. (+info)