Tadashi Miyahara

Glutathione-dependent inactivation of sodium-dependent phosphate transport across rat renal brush-border membrane

Thiol/disulfide is fundamental in protein function; we previously observed an inhibitory effect of thiol oxidants on the Na-dependent phosphate (Pi) uptake into renal brush border membrane vesicles (BBMV). We examined whether oxidation of glutathione (GSH) is involved in the mechanism. Vesicular thiols were measured by liquid chromatography. BBMV were incubated with reagents before an influx of Pi. Diamide (5 mM) reduced the capacity of the Pi uptake. Subsequent treatment with dithiothreitol (5 mM) blocked the inhibitory effect of diamide. Vesicular GSH was not modified only by the incubation, whereas it was oxidized by the treatment with diamide, and reduced by dithiothreitol. Furthermore, in vivo treatment with cAMP provided GSH-depleted BBMV without any influence on Pi uptake. Diamide did not inhibit the transport of Pi into GSH-depleted vesicles, but it did inhibit the uptake when GSH was introduced into the vesicles. In conclusion, a GSH-dependent mechanism is involved in the inhibitory effect of diamide on sodium-dependent Pi transport across the renal brush-border membrane.

Impaired Lactate Production by Skeletal Muscle with Anaerobic Exercise in Patients with Chronic Renal Failure

The lactate concentration in antecubital venous blood was determined in 33 patients before and after ischemic forearm exercise. Before exercise, there wa no significant difference in serum lactate level between uremic patients and controls. However, after ischemic exercise the means serum lactate level in uremic patients was significantly lower than that of controls. The results may lead to the conclusion that uremic patients have a markedly reduced ability to form lactate with anaerobic exercise probably due to inhibition of glycolytic enzymes of skeletal muscle.

1,25-Dihydroxyvitamin D stimulates sodium-dependent phosphate transport by renal outer cortical brush-border membrane vesicles by directly affecting membrane fluidity

We examined the effects of several forms of vitamin D added to renal brush-border membrane suspensions on phosphate and glucose transport and on membrane fluidity. The 1,25-D stimulated and the other vitamin D decreased phosphate uptake. In contrast, glucose uptake was not affected by the treatment of vitamin D. The 1,25-D resulted in a significant shift of the lower transition temperature in Arrhenius plots for phosphate, but not for glucose uptakes, from 15 degrees C to 11.5 degrees C. These data indicate that the 1,25-D may alter membrane fluidity, limited to the phosphate transporter, thus affecting the phosphate uptake.

Experimental Drug-Induced Allergic Nephritis Mediated by Antihapten Antibody

Experimental drug-induced allergic nephritis (DIAN) was mediated by an antihapten antibody. It has been postulated that DIAN is induced by cellular and humoral mechanisms. We tried to induce DIAN in mice, where the mechanism depends on humoral immunity. The first attempt was made in mice actively producing antibodies against cephem antibiotics, i.e. cephalothin (CET). Acute interstitial nephritis (AIN), morphologically similar to human disease, was obtained by injection of a CET-protein conjugate into the renal cortex in mice producing anti-CET-IgE and IgG antibodies. AIN could also be induced when normal mice, passively given anti-CET IgG antibody, received a subsequent intrarenal challenge with CET-protein conjugate. These preliminary results indicate that IgG antibody has an important role in the genesis of DIAN. Further experiments were performed with monoclonal antibodies directed against haptens instead of antibiotics in order to clarify the Ig isotype concerned. In mice passively given anti-Dansyl-IgG2a or anti-NP-IgG2a monoclonal antibodies, a challenge with an appropriate hapten-protein conjugate into the renal cortex resulted in AIN. However, transfer of anti-Dansyl-IgE or anti-DNP-IgE monoclonal antibodies, followed by challenge, did not induce AIN. In the experimental systems described, the involvement of a cellular immune mechanism is excluded. The results suggest that IgG, but not IgE antibody, is essential for the induction of DIAN by humoral immune mechanism.

The effects of vasoactive agents on the proliferation of vascular smooth muscle cells grown in vitro.

The present study was designed to investigate the effect of vasoactive agents on cellular proliferation in serially passed cultured vascular smooth muscle cells (VSMC). A substantial reduction in the number of vascular smooth muscle cells was observed with the addition of nifedipine, nicorandil, bunazocine and labetalol compared with that in a control sample. Furthermore, noradrenaline significantly increased the number of vascular smooth muscle cells. In contrast, neither propranolol nor captopril had any effect on number of vascular smooth muscle cells. The cell size, measured as water volume of vascular smooth muscle cells based on the equilibrium distribution of 3-O-(14C-methyl)-D-glucose, did not differ between treatments with the above-mentioned agents. It is suggested that in addition to a known calcium-mediated mechanism, an α-receptor-mediated property could be involved in the proliferation of vascular smooth muscle cells and that clinical use of a calcium antagonist or an α-blocker might be useful to prevent the hyperproliferation of vascular smooth muscle cells commonly seen in the vascular walls of patients with hypertension.

Determination of Uric Acid in Human Serum: Reversed-Phase Liquid Chromatography with Electrochemical Detection

Abstract A method for the simultaneous determination of uric acid in human serum by reversed-phase high-performance liquid chromatography with electrochemical detection has been developed. Human serum (0.5 ml) was mixed with 0.5 ml of 0.2 N perchloric acid solution and the mixture was centrifuged at 3,000 g for 20 min. An aliquot (10 μl) of the supernatant (deproteinized human serum) was injected into the chromatographic system employed in this study. The assay limit for quantitation was about 10 pg for uric acid. Complete separation of uric acid was achieved in about 8 min under the present chromatographic conditions.

Phase I study of EST, a new thiol protease inhibitor. The 2nd report: Safety and pharmacokinetics in continuous administration.

EST is a specific thiol protease inhibitor newly synthesized as a drug for muscular dystrophy.Following the first Phase I study of EST single dose (First report), the second Phase I study on EST continuous administration was performed in healthy adult male volunteers to investigate its safety and pharmacokinetics.In the first stage, 100mg was administered 3 times a day after meals for 1 day, and in the next stage, 100 mg was administered 3 times a day after meals for 7 consecutive days.No change due to EST was found from the observation of the subjective and objective symptoms and clinical tests.EST was detected as E-64-c (effective form of EST) in serum and urine after oral administration. No accumulation of EST was observed after continuous administration, and approximately 30% of total EST was collected in urine.

Simple Methods for the Determination of Methylguanidine and Guanidinosuccinic Acid in Biological Fluids

It is recognized that guanidino derivatives significantly accumulate in uremic patients and contribute to the toxic manifestations of uremia. Among those compounds, both methylguanidine (MG) and guanidinosuccinic acid (GSA) have been especially interesting for their role as uremic toxinsl. As the implications of MG and GSA as uremic toxins has become more obvious, routine measurement of those substances in biological fluids has assumed increasing importance in managing uremic patients to observe the effects of treatment.

[A case of bladder-rectro fistula complicated with intermittent disturbance of consciousness caused by hyperchloremic metabolic acidosis].

本例は子宮癌手術後に膀胱直腸瘻が形成され,その瘻孔が局所の腫脹やsludgeの状態により閉鎖と開放が繰り返され,其の都度,急激な代謝性アシドーシスと代償性の呼吸性アルカロ一シスを合併する混合性酸塩基平衡障害をきたし,意識障害を繰り返した症例である.膀胱直腸瘻では高C1性アシざ一シスを呈するが,繰り返す意識障害を示す症例はまれである.

Autonomic dysfunction in patients with chronic renal failure

指尖容積脈波のデジタル処理解析による交感・副交感神経機能検査法を用いて慢性腎不全患者の自律神経機能を検討した. 対象は慢性腎炎 (62例), 嚢胞腎 (3例), 腎盂腎炎 (2例), 痛風腎 (1例) 由来の慢性腎不全68例 (非透析群17例, 血液透析群30例, CAPD群18例, 腎移植群3例) で, 糖尿病, SLE等の全身性疾患による腎不全例は除外した. 指尖容積脈波は安静臥位で非シャント側, 第2指より2分間連続記録, デジタル処理解析し, 脈波波高変動係数 (CVWH), 脈拍間隔変動係数 (CVPP) を算出した.CVWH, CVPPはそれぞれ腎不全群7.44±3.58, 2.41±0.94, 非透析群7.92±3.68, 2.88±0.94, 血液透析群7.57±4.04, 2.29±0.76, CAPD群6.69±2.96, 1.96±0.83, 腎移植群8.20±1.92, 3.70±1.32であった. CVWHは健常群に比して腎不全各群で有意の低下を示し, CVPPは非透析群では健常群との間に有意差はないものの低値を示す例が多く認められた. 透析群では明らかに有意の低下を示した. また, 透析法別にみた群間比較に有意差を認めなかった. CVWHとCVPPの関係を見ると腎不全例, 透析例で有意の相関を認めた.以上より, 今回検討した慢性腎不全例のCVWH, CVPPは共に低下し, 交感・副交感神経機能に障害を認めた. 非透析群間に差を認めなかったことから, 腎不全で認められる自律神経障害は透析療法では改善困難であると考えられた. また, 腎不全群と透析群のCVWHとCVPPとに相関が認められたことより交感・副交感神経が同時に障害されることが推察された.