Yoshifumi Fukuhara

Prospective Randomized Study Evaluating the Efficacy of the Spherical Adsorptive Carbon AST-120 in Chronic Kidney Disease Patients with Moderate Decrease in Renal Function

Aims: We studied whether adding the spherical adsorptive carbon AST-120 to conventional treatments is effective in inhibiting progression of chronic kidney disease (CKD) at the stage of moderate decrease in renal function. Methods: 43 CKD patients with moderately impaired renal function indicated by glomerular filtration rate (GFR) of 20–70 ml/min as measured by non-radiolabeled iothalamate clearance method were enrolled in the study. 26 patients showing a decrease of GFR by 5 ml/min during a 1-year observation period were randomized to receive ongoing treatments only (control group, 12 cases) or with AST-120 co-administered with ongoing treatment (AST-120 group, 14 cases). The intervention period was 1 year and the change in GFR was the primary evaluation variable. Results: The mean changes of GFR per month (ΔGFR) in the intervention period were not significantly different between both groups. However, when comparing the ΔGFR in the observation and intervention periods for each group, the rate of decline in GFR was significantly retarded (p < 0.001) in the AST-120 group while no significant difference was observed in the control group. Conclusion: These results suggest that co-administration of AST-120 with conventional treatments retards decline in renal function in CKD patients with moderate decrease in renal function.

Effect of arginine or creatinine administration on the urinary excretion of methylguanidine.

The metabolic pathway of methylguanidine (MG) is mainly speculated from the change in urinary excretion of MG in the arginine (Arg)-injected normal rat, the creatinine (Cr)-injected normal rat, and the Arg-injected uremic rat. 15N-Arg was ingested to 2 uremic patients. Arg administration resulted in marked increase in urinary MG excretion both in the uremic rat and patient, but not in the normal rat. In the first phase of the 15N-Arg ingestion experiment, a rapid rise of 15N atom percent excess of urinary MG was observed in the uremic patient. In the second phase of this study, after 24 h of 15N-Arg ingestion, the 15N atom percent excess of urinary Cr and that of MG closely paralleled. These findings imply that there might be two metabolic origins of MG: one is a formation of MG from Arg itself or an Arg metabolite other than Cr, the other a pathway producing MG via Cr. The former is compatible with the hypothesis by Cohen.

Comparative effects of cyclosporine A and FK-506 on endothelin secretion by a cultured renal cell line, LLC-PK1.

Cyclosporine A (CSA) stimulated endothelin secretion by a cultured renal epithelial cell line, LLC-PK1. A less nephrotoxic immunosuppressant (FK-506) did not affect endothelin secretion. Putative endothelin converting enzyme inhibitors or specific receptor antagonists may therefore prevent CSA nephrotoxicity.

Cerebral Magnetic Resonance T2 High Intensities in End-Stage Renal Disease

BACKGROUND AND PURPOSE The pathophysiological mechanisms that cause cerebral MR T2 high intensities in end-stage renal disease (ESRD) are unclear. We evaluated the incidence and the risk factors of T2-weighted MR brain high intensities in patients with ESRD. METHODS We examined the degree of T2-weighted MR brain high intensities (high intensity score) and determined the variables that had an independent association with the occurrence of high intensities in 38 patients with ESRD before chronic dialysis treatment, 173 patients with essential hypertension, and 72 normotensive control subjects. RESULTS The whole brain high intensity score was significantly higher in patients with ESRD than in the control subjects, but there was no significant difference in high intensity score between the ESRD and the hypertensive groups. Age, hypertension, and smoking were significant independent predictors of high intensities in a multiple logistic regression model. The distribution pattern of high intensities in ESRD patients was very similar to that obtained from hypertensive patients; the high intensity score was highest in the corona radiata and was lowest in the cerebellum. CONCLUSIONS T2 high intensities on MR images of ESRD may reflect subcortical small-vessel alterations induced by hypertension.

Decrease in the fluidity of brush-border membrane vesicles induced by gentamicin a spin-labeling study

In our previous paper (Horio et al., Biochim Biophys Acta 858: 153-160, 1986), we reported that the addition of gentamicin in vitro to rabbit renal brush-border membrane vesicles decreases the apparent Vmax of Na+-dependent D-glucose transport without affecting the apparent Km. In the present study, we investigated the effects of gentamicin on the physical state of spin-labeled rabbit renal brush-border membranes, using electron spin resonance spectrometry. Brush-border membrane vesicles were prepared from outer cortex (mainly contains early proximal tubule) and outer medulla (containing primarily late proximal tubule), and the gentamicin toxicities in both preparations were compared. Significant decreases were observed in the membrane fluidity of 5 mM gentamicin-treated brush-border membranes. The fluidity of outer cortical brush-border membranes was affected at both 25 degrees and 35 degrees, whereas that of outer medullary membranes was affected only at 35 degrees. Two different stearic acid spin labels revealed that gentamicin affected the fluidity only in the superficial region of the membranes. We also demonstrated that the gentamicin-induced decreases in Na+-dependent D-glucose transport and in the membrane fluidity were recovered by washing gentamicin-treated brush-border membranes. We suggest that gentamicin binds to the superficial region of brush-border membranes and inhibits Na+-dependent D-glucose transport across brush-border membranes through the decrease in the membrane fluidity.

Pharmacokinetic and Pharmacodynamic Interactions between Furosemide and Hydrochlorothiazide in Nephrotic Patients

We examined the response of 8 patients with nephrotic syndrome (creatinine clearance 70.4 +/- 16.0 ml/min) to oral furosemide (F; 40 mg) in the absence (control) and in the presence of oral hydrochlorothiazide (HCT; 100 mg). In the 24-hour period after oral F, HCT was shown to increase urine volume and urinary sodium and chloride excretion. Increment was most significant during the 12- to 24-hour period. Enhancement of the diuresis with HCT was associated neither with a significant increase in the area under the curve of plasma F concentration nor an increase in urinary F excretion. Urinary excretion of glucuronidated F, one of the main metabolites of F, however, was decreased with HCT. In summary, HCT significantly enhanced the response to F in nephrotic patients.

Stimulatory effect of thrombin on endothelin-1 production in isolated glomeruli and cultured mesangial cells of rats.

To determine whether endothelin-1 (ET-1) is released in close proximity to its binding sites on glomerular mesangial cells, and also to elucidate the regulatory factors responsible for its release, we measured immunoreactive ET-1 (ir-ET-1) in the incubation media of isolated glomeruli and cultured mesangial cells of rats using enzyme immunoassay under both basal and thrombin-stimulated conditions. ir-ET-1 was released time-dependently, from isolated glomeruli and cultured mesangial cells. Thrombin (2 U/ml) stimulated the release from both preparations. The release of immunoreactive big endothelin-1 (ir-big ET-1), which was assayed by using enzyme immunoassay, was also time-dependent, and the release was increased by thrombin (2 U/ml; at 4 h, 8 h, and 24 h) in cultured mesangial cells. The releases of big ET-1 and its converted product ET-1 from mesangial cells, an established target for ET-1, suggests that ET-1 acts as an autocrine factor for the cells.

Furosemide Accelerates Gentamicin Accumulation in Cultured Renal Cells (LLC-PK1 Cells)

Furosemide is known to potentiate gentamicin nephrotoxicity. The mechanism of potentiation is unclear. In our previous studies, we demonstrated that furosemide enhanced gentamicin accumulation in rabbit renal tissues when injected as a bolus [Kidney int. 33:363, 1988] or repeatedly subcutaneously [Diuretics II, Elsevier, New York 1987, pp.693]. In this study, we evaluated the effects of furosemide on gentamicin accumulation in cultured renal cells (LLC-PK1) and hepatoma cells (H4IIE). Thus, we excluded effects secondary to furosemide-elicited hemodynamic changes. Seven days after seeding, the culture medium was exchanged for medium containing 1 mM gentamicin alone [G] or 1 mM gentamicin +1 mM furosemide [GF]. In LLC-PK1 cells, gentamicin concentration in [GF] was significantly higher than that in [G], while gentamicin was not detected in H4IIE cells with or without furosemide. We conclude that furosemide can accelerate gentamicin accumulation in renal tissues and potentiate gentamicin nephrotoxicity.

Gentamicin inhibits Na+-dependent D-glucose transport in rabbit kidney brush-border membrane vesicles

We studied the effect of gentamicin on Na+-dependent D-glucose transport into brush-border membrane vesicles isolated from rabbit kidney outer cortex (early proximal tubule) and outer medulla (late proximal tubule) in vitro. We found the same osmotically active space and nonspecific binding between control and gentamicin-treated brush-border membrane vesicles. There was no difference in the passive permeability properties between control and gentamicin-treated brush-border membrane vesicles. Kinetic analyses of D-glucose transport into 1 mM gentamicin-treated brush-border membrane vesicles demonstrated that gentamicin decreased Vmax in the outer cortical preparation, while it did not affect Vmax in the outer medullary preparation. With regard to Km, there was no effect of gentamicin in any vesicle preparation. When brush-border membrane vesicles were incubated with higher concentrations of gentamicin, Na+-dependent D-glucose transport was inhibited dose-dependently in both outer cortical and outer medullary preparations. Dixon plots yield inhibition constant Ki = 4 mM in the outer cortical preparation and Ki = 7 mM in the outer medullary preparation. These results indicate that the Na+-dependent D-glucose transport system in early proximal tubule is more vulnerable to gentamicin toxicity than that in late proximal tubule.

The mechanism of decreased Na+-dependent d-glucose transport in brush-border membrane vesicles from rabbit kidneys with experimental Fanconi syndrome

In our previous paper (Yanase, M. et al. (1983) Biochim. Biophys. Acta 733, 95-101) we reported that the Na+-dependent D-glucose uptake into brush-border membrane vesicles is decreased in rabbits with experimental Fanconi syndrome (induced by anhydro-4-epitetracycline). In the present paper we investigate the mechanism underlying this decrease. D-Glucose is taken up into the osmotically active space in anhydro-4-epitetracycline-treated brush-border membrane vesicles and exhibits the same distribution volume and the same degree of nonspecific binding and trapping as in control brush-border membrane vesicles. The passive permeability properties of control and anhydro-4-epitetracycline-treated brush-border membrane vesicles are shown to be the same as measured by the time-dependence of L-glucose efflux from brush-border membrane vesicles. D-Glucose flux was measured by the equilibrium exchange procedure at constant external and internal Na+ concentrations and zero potential. Kinetic analyses of Na+-dependent D-glucose flux indicate that Vmax in anhydro-4-epitetracycline-treated brush-border membrane vesicles (79.3 +/- 7.6 nmol/min per mg protein) is significantly smaller than in control brush-border membrane vesicles (141.3 +/- 9.9 nmol/min per mg protein), while the Km values in the two cases are not different from each other (22.3 +/- 0.9 and 27.4 +/- 1.8 mM, respectively). These results suggest that Na+-dependent D-glucose carriers per se are affected by anhydro-4-epitetracycline, and that this disorder is an important underlying mechanism in the decreased Na+-dependent D-glucose uptake into anhydro-4-epitetracycline-treated brush-border membrane vesicles.