Shozo Koshikawa

Calcimimetic Compound Upregulates Decreased Calcium-Sensing Receptor Expression Level in Parathyroid Glands of Rats with Chronic Renal Insufficiency

The reduced expression level of the calcium-sensing receptor (CaR) is attributed to the hyposensitivity of parathyroid cells to extracellular calcium concentration [Ca2+]o, which plays a crucial role in the pathogenesis of secondary hyperparathyroidism (SHPT) in patients and rats with chronic renal insufficiency (CRI). Calcimimetic compounds have been demonstrated to improve the decreased sensitivity of CaR to extracellular calcium concentration and to suppress both parathyroid hormone (PTH) oversecretion and parathyroid cell proliferation. However, the effect of calcimimetics on the reduced CaR expression level in parathyroid cells in CRI remains unclarified. The aim of this investigation was to examine the effect of the calcimimetic compound NSP R-568 (R-568) on the CaR expression in the parathyroid cells of rats with experimental CRI. Subtotally nephrectomized rats were fed a high-phosphorus diet for 8 (n = 12; Nx-8 group) or 9 wk (n = 11; Nx-9 group) to induce severe SHPT. Another group of uremic rats were fed a high-phosphorus diet for 8 wk and then orally administered R-568 (100 micromol/kg body wt) once a day for 7 d (n = 11; Nx+R-568 group). Sham-operated rats that were fed a standard diet for 9 wk were used as controls (n = 8). R-568 treatment induced a significant reduction in plasma PTH level with significant decrease in serum calcium and without change in serum phosphorus concentration. Serum 1,25(OH)2D3 level was not affected by R-568 administration. CaR mRNA and protein levels in the Nx-8 and Nx-9 groups significantly decreased compared with those in the controls; however, no significant difference in these parameters was observed between the Nx-8 and Nx-9 groups. In the Nx+R-568 group, CaR mRNA and protein levels significantly increased compared with those in either the Nx-8 or Nx-9 group. R-568 was effective in reducing the number of proliferating cell nuclear antigen-positive cells along with parathyroid gland growth suppression in the Nx+R-568 group compared with that in the Nx-9 group. The results suggest that the calcimimetic compound R-568 upregulates decreased CaR expression, and the upregulation possibly has an enhancement effect on PTH secretion and parathyroid cell hyperplasia through the improved sensitivity of CaR to [Ca2+]o.

Current status of renal replacement therapy in Japan

The study of the current status of renal replacement therapy in Japan is based on the analysis of data from the registry reports for regular dialysis therapy and kidney transplantation. The total number of patients receiving regular dialysis therapy was 123,926 at the end of 1992: 117,809 (95.1%) on hemodialysis and 6,117 (4.9%) on peritoneal dialysis. The primary diseases of newly accepted patients were chronic glomerulonephritis (42.2%), diabetic nephropathy (28.4%), nephrosclerosis (5.9%), polycystic kidney disease (2.7%), chronic pyelonephritis (1.6%), and others. The number of kidney transplant patients in Japan was 8,384 at the end of 1991: 6,154 (73.4%) received a living donor transplantation and 2,230 (26.9%) received a cadaver donor transplantation. Overall 5-year survival rates of dialysis patients were 60.4%: 69.7% for chronic glomerulonephritis, 41.7% for diabetic nephropathy, 39.6% for nephrosclerosis, 73.6% for diffuse polycystic kidney disease, and 66.6% for chronic pyelonephritis. The causes of death of dialysis patients were heart failure (31.1%), cerebrovascular accident (13.6%), infectious diseases (11.3%), malignancies (7.1%), cachexia/uremia (6.7%), myocardial infarction (5.8%), and others. The gross mortality rate of dialysis patients was increased in cases of less than 4 hours of the average length of each dialysis session, less than 4% and more than 9% of the average weight loss during each dialysis session, less than 1.0 of Kt/V, and less than 0.9 and more than 1.7 g/kg/d of protein catabolic rate. Overall 5-year patient and graft survival rates of kidney transplant patients since 1964 were 82.7% and 60.3%: 84.4% and 65.0% in living donor cases, and 77.4% and 46.2% in cadaver donor case, respectively. Those since 1983 were 90.1% and 68.2%: 91.3% and 72.6% in living donor cases, and 87.8% and 59.3%, respectively. Graft survival rates were superior in cases treated with combined steroid, cyclosporine and azathioprine or mizoribine, to those treated with other immuno-suppressive regimens, and they decreased as the number of HLA-A, -B and -DR increased.

Nafamostat Mesilate: A Regional Anticoagulant for Hemodialysis in Patients at High Risk for Bleeding

107 hemodialysis patients at high risk for intradialytic bleeding due to previous surgery or active bleeding from other sites were treated with nafamostat mesilate (FUT-175; FUT) as hemodialysis anticoagulant for 2 weeks. In contrast to heparin. FUT prolonged clotting times only in the extracorporeal circuit. Clotting times were not prolonged even at the conclusion of the treatment, and bleeding from the puncture site after removal of the needle was shorter than with heparin. The exacerbation of bleeding by hemodialysis was noted in only 21 out of 573 hemodialysis procedures (3.7%), and 134 of 145 hemodialysis procedures (92.4%) with active bleeding were successfully completed without increasing the bleeding. Adverse effects of FUT were noted in only 6 cases (5.6%) or 1.2% of HD procedures. These results indicate that FUT is a very useful anticoagulant for HD, especially in patients with high risk of bleeding.

Activation of calcium-sensing receptor accelerates apoptosis in hyperplastic parathyroid cells

Calcimimetic compounds inhibit not only parathyroid hormone (PTH) synthesis and secretion, but also parathyroid cell proliferation. The aim of this investigation is to examine the effect of the calcimimetic compound NPS R-568 (R-568) on parathyroid cell death in uremic rats. Hyperplastic parathyroid glands were obtained from uremic rats (subtotal nephrectomy and high-phosphorus diet), and incubated in the media only or the media which contained high concentration of R-568 (10(-4)M), or 10% cyclodextrin, for 6h. R-568 treatment significantly suppressed medium PTH concentration compared with that of the other two groups. R-568 treatment not only increased the number of terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling assay-positive cells, but also induced the morphologic changes of cell death determined by light or electron microscopy. These results suggest that CaR activation by R-568 accelerates parathyroid cell death, probably through an apoptotic mechanism in uremic rats in vitro.

Antithrombotic therapy with ticlopidine in chronic renal failure patients on maintenance hemodialysis -a multicenter collaborative double blind study-

Abstract The effect of a new inhibitor of platelet aggregation, ticlopidine, at a daily oral dose of 200mg, was investigated on prevention of thrombotic obstruction of the arterio-venous shunts or vascular grafts in 107 uremic patients under chronic hemodialysis: the patients were those who had suffered from frequent thrombotic episodes in their blood accesses. The study was conducted in a double blind fashion with an inactive placebo. Frequency of clot removal was significantly (p

Clinical effect of recombinant human erythropoietin on anemia associated with chronic renal failure. A multi-institutional study in Japan.

Clinical effect and safety of recombinant human erythropoietin (r-HuEPO) were evaluated in 66 hemodialysis patients with intractable anemia. Initially, 50U/kg dry weight (DW) of r-HuEPO was administered intravenously at the end of every hemodialysis procedure for 4 weeks, then the dosage was increased to 100 and 200U/kg DW for poor responders. The patients’ hematocrits rose from 19.8 ± 2.3% (pretreatment) to 30.2 ± 4.9% after 12 weeks. From 206 U of blood transfusion requirement in the 3-month period before the study, only 34 U were needed after treatment. Serum iron and ferritin levels fell significantly during the study, and iron storage was considered to be one of the decisive factors in the response to r-HuEPO. Blood pressure rose in the course of r-HuEPO administration, but uncontrollable hypertension was rarely observed. There was no significant adverse effect of r-HuEPO except for this mild hypertension. These results indicate that r-HuEPO is an excellent therapeutic aid for the anemia associated with chronic renal failure.

Effects of Recombinant Human Erythropoietin and Correction of Anemia on Platelet Function in Hemodialysis Patients

To clarify the effects of correction of anemia with recombinant human erythropoietin (r-HuEPO) on the hemostatic defects in uremia, hemostatic parameters were examined in 18 hemodialysis patients with renal anemia. Anemia improved significantly 12 weeks after r-HuEPO therapy (stage II) compared to pretreatment (stage I) and 6 weeks discontinuation (stage III) periods. Platelet count did not change among the three stages, however, mean platelet volume increased significantly at stage II in comparison with stage I. Ivy bleeding time (BT) significantly shortened at stage II and prolonged again at stage III. Although there were no significant changes in platelet aggregation, plasma TxB2, 6-keto-PGF1 alpha, F.VIII:C and F.VIII:Ag levels throughout the study, platelet adhesion and von Willebrand factor (vWf):Ag significantly increased at stages II and III. Augmentations in these parameters were more remarkable in BT-shortened patients (n = 12) than in the BT-unchanged group. These results indicate that correction of anemia with r-HuEPO brought about improvement in uremic hemostatic defect via the increase in red cell volume and vWf:Ag, and new production of platelets, reflected by the improvement in platelet adhesion.

Recent progress in management of secondary hyperparathyroidism of chronic renal failure.

Recent progress in cellular and molecular biology has had a great impact on our understanding of parathyroid hormone-vitamin D physiology and of the pathogenesis of secondary hyperparathyroidism in chronic renal failure and made possible the development of new therapeutic approaches for management of bone disease in dialysis patients. Management of parathyroid hyperplasia by calcitriol pulse therapy is one example. Suppression of parathyroid hyperfunction by other vitamin D analogues was also proposed, and some of these analogues are now under clinical trial. Further, percutaneous ethanol injection into hyperplastic parathyroid glands under ultrasonographic guidance has become the choice practical procedure under certain clinical settings and can be an effective alternate to surgical parathyroidectomy. In this article, we review selected and pertinent progress in the pathogenesis and management of secondary hyperparathyroidism and parathyroid hyperplasia, major causes of morbidity in chronic dialysis patients, emphasizing the important contributions made by laboratory research and critical clinical observations.

Autoregulation of Renal Blood Flow in Streptozocin-Induced Diabetic Rats

Autoregulation of renal blood flow (RBF) was studied in male Wistar rats. We studied 11 control rats, 11 rats with severe streptozocin (STZ)-induced hyperglycemia (diabetic group), and 10 moderately hyperglycemie rats made diabetic by injection of STZ but given 2–8 U s.c. insulin daily (insulin-treated group). RBF was measured by an electromagnetic flowmeter during stepwise reduction of renal perfusion pressure 4–8 wk after injection of STZ (older group). RBF autoregulation of the diabetic group was impaired compared with the control group. In the insulin-treated group, autoregulatory capability was less attenuated than in the diabetic group. The average autoregulatory index (ARI) of the diabetic group (0.61 ± 0.05) was greater than that of the control (0.24 ± 0.02, P < .01) and the insulin-treated (0.33 ± 0.07, P < .05) groups. To study the relationship between autoregulation and the duration of diabetes, an autoregulatory study was also made in a group of 22 rats (11 diabetic and 11 control) that were tested 2–3 wk after injection of STZ (younger group). The ARI in the younger diabetic group was smaller than that in the older diabetic group (P < .05). The results suggest that in uncontrolled diabetes RBF fluctuates with blood pressure change, and protection against hypertensive injury of glomerular capillaries may be diminished. Autoregulatory disability develops with time, and insulin treatment diminishes impairment of autoregulation. These findings may also explain the adverse consequences of hypertension on the progression of diabetic nephropathy in poorly controlled diabetes.

Protective Effect of an Oral Adsorbent on Renal Function in Chronic Renal Failure: Determinants of its Efficacy in Diabetic Nephropathy

Abstract:  Large‐scale clinical trials have shown that the oral adsorbent AST‐120 improves renal function and delays the initiation of dialysis in chronic renal failure (CRF) secondary to chronic glomerulonephritis. If renal failure progresses via common mechanisms, then the same effects can be expected in diabetic nephropathy. However, no study on diabetic nephropathy has been reported. Thus, we enrolled patients with statistically significant progression of CRF secondary to diabetic nephropathy, and analyzed the changes in renal function after AST‐120 therapy, and the clinical factors associated with response to therapy. We enrolled 276 patients with diabetic nephropathy, whose serum creatinine (Scr) had increased from 3.4 to 4.5 mg/dL during the 4.5 ± 3.7 months prior to the study. These patients took AST‐120 at a dose of 5.0 ± 1.4 g/day for 6 months. The clinical data were analyzed by dividing the patients into three groups based on the changes in Scr after AST‐120 therapy, with responders showing a decrease (N = 82), partial responders showing <1.5‐fold increase (N = 144), and non‐responders showing ≥1.5‐fold increase (N = 50). AST‐120 significantly lowered the slope of 1/Scr–time line, suggesting that AST‐120 suppressed the progression of renal impairment. No responders required dialysis, whereas 24.3% of the partial responders and 36.0% of the non‐responders started dialysis therapy. In responders, the 1/Scr–time slope showed a negative‐to‐positive shift and serum urea nitrogen decreased significantly, whereas the improvement was moderate in partial responders and minimal in non‐responders. Among responders, AST‐120 therapy significantly improved renal function despite the presence of hypoproteinemia, hyperlipidemia, anemia or hypertension in many patients. The beneficial effect of AST‐120 was significantly more marked in patients with blood pressure controlled within the normal ranges and hematocrit maintained at 30% or above. AST‐120 reversed renal dysfunction or delayed the initiation of dialysis therapy in patients with progressive aggravation of CRF secondary to diabetic nephropathy, independent of hypoproteinemia, hyperlipidemia, anemia and hypertension. Active use of AST‐120 may be recommended in patients with good control of blood pressure and hematocrit above 30%.