Role of endogenous endothelin and nitric oxide in tubuloglomerular feedback

To elucidate the roles of endogenous endothelin (ET) and nitric oxide (NO) in tubuloglomerular feedback (TGF), the effects of FR139317, a specific ET-A receptor antagonist, and NG-nitro-L-arginine (L-NNA), a NO synthase inhibitor on TGF were studied in Sprague-Dawley rats. FR139317 (1.5 mg/kg/hr i.v.) reversed the systemic pressor and renal vasoconstrictor responses induced by ET-1 (2 nmol/kg/hr i.v.), but did not alter the early proximal flow rate (EPFR) reduction in response to a loop perfusion with an artificial tubular fluid at 40 nl/min (47 +/- 3 vs. 47 +/- 3% in controls). L-NNA (0.2 mg/kg + 2 micrograms/kg/min i.v.) had no effect on systemic blood pressure (BP), renal hemodynamics or EPFR measured at zero perfusion (31 +/- 2 vs. 31 +/- 2 nl/min in controls), but enhanced the EPFR reduction during loop perfusion to 77 +/- 3%. Loop perfusion with 10(-3) M L-NNA in perfusate also increased the EPFR reduction to 70 +/- 7%. In conclusion, inhibition of NO synthesis enhances the TGF-mediated reduction of nephron GFR. This indicates an active participation of endogenous NO in the control of afferent arteriolar tone. endogenous ET does not influence TGF via the ET-A receptor.

[Synthesis and antibacterial properties of quinoxaline 1,4-dioxide derivatives]

Novel quinoxaline 1,4-dioxide derivatives were synthesized from benzofuroxans and the enolic form of 1,3-diketones or 3-oxoalkanoic esters or 3-oxoalkanamides or butanedioic esters catalyzed by silica gel or molecular sieves and their antibacterial activities were evaluated. As the results of antibacterial screening tests in vitro, quinoxaline 1,4-dioxides revealed strong activities against Bacteroides fragilis.

Activation of two Cynops genes, fork head and sonic hedgehog, in animal cap explants

We have isolated cDNAs of sonic hedgehog (shh) and fork head from Cynops (Japanese newt) embryo. Their expression was investigated in relation to mesoderm induction by activin and basic fibroblast growth factor (bFGF). Different from these homologs in Xenopus, they are activated not only by activin but also by bFGF in animal cap explants, showing a difference of animal pole cells in responsiveness to bFGF between Cynops and Xenopus. We also investigated the involvement of fork head in shh activation. The expression of shh was activated in animal caps which overexpressed either of two Xenopus fork head homologs, pintallavis/XFD-1 or XFKH-1/XFD-1', indicating that fork head up-regulates the transcription of shh in Cynops embryo.

Effects of ACE inhibition and beta-blockade on collagen remodelling in the heart of Bio 14.6 hamsters

1. The effects of angiotensin converting enzyme (ACE) inhibition and beta-blockade on collagen in the heart and on plasma catecholamines and tissue angiotensin (Ang) I and II were examined in Bio 14.6 Syrian hamsters. Male hamsters (76-79 days old) were given low-dose enalapril (3 mg/kg per day), high-dose enalapril (30 mg/kg per day), atenolol (50 mg/kg per day) or vehicle for 65 days. Age and sex matched healthy F1b hamsters were used as controls. Collagen concentration was determined by measuring hydroxyproline content and the relative proportion of type I, III, and V collagens was obtained by non-interrupted sodium dodecyl polyacrylamide gel electrophoresis (SDS-PAGE). Per cent collagen area (PCA) was measured by pixel counting in myocardial tissue by a personal computer. 2. Although heartweight (HW) and bodyweight (BW) in F1b controls were significantly higher compared with drug-treated groups and vehicles, the HW/BW ratio in cardiomyopathic Bio 14.6 hamsters tended to be high compared with F1b controls and was decreased by each drug treatment. 3. Collagen concentration, total collagen content and PCA in the heart of Bio 14.6 hamsters were significantly higher than F1b controls. Collagen concentration and total collagen content were significantly decreased in all drug-treated groups compared with vehicles. 4. The proportion of type I collagen tended to decrease while that of type III collagen tended to increase in all drug-treated groups compared with vehicles. Type V collagen in vehicle-treated group was significantly higher than in F1b controls, while it tended to decrease in all drug-treated groups compared with vehicles. 5. Plasma concentrations of catecholamines (adrenaline and noradrenaline) were decreased significantly by atenolol and high-dose enalapril, but not by low-dose enalapril. Tissue AngI remained unaltered in any of the drug-treated hamsters. Tissue AngII was decreased by the high-dose enalapril and beta-blockade, and tended to be decreased by low-dose enalapril treatment. 6. These results reveal that enalapril and atenolol produced similar beneficial effects on collagen remodelling in Bio 14.6 hamsters by decreasing the total amount of collagen, and also by changing collagen phenotypes through the inhibition of the renin-angiotensin system. Both drugs also improved myocardial morphological integrity.

Endothelin induced collagen remodeling in experimental pulmonary hypertension

To investigate pathophysiological roles of endothelin-1 (ET-1) in collagen remodeling in pulmonary hypertension, we measured: (a) mRNA expression, concentration, localization of ET-1; (b) changes in types and content of collagen in the lung; (c) and confirmed direct effects of ET-1 on type V collagen metabolism in vascular smooth muscle cells. Monocrotaline-treated rats showed pulmonary hypertension with medial hypertrophy and perivascular fibrosis of pulmonary arteries. At the progressive stage of pulmonary hypertension, both ET-1 levels and its mRNA expression in the lung increased. Total collagen in the lung rose markedly with a higher rate of increase in type V collagen. ET-1, which exists in vascular smooth muscle cells, other perivascular cells and endothelium, stimulated type V collagen production. Our results suggest that local production of ET-1 in the lung contributes to progression of pulmonary hypertension through changes in phenotypes and content of collagen.

[Microcirculation in renal interstitium]

Microcirculation in the renal interstitium plays an important role in the regulation of urinary sodium excretion and thus in the control of blood pressure. An increase in renal interstitial hydrostatic pressure caused by renal perfusion pressure elevation induces pressure natriuresis by decreasing tubular reabsorption. Chronic NO inhibition in the medullary interstitium decreases medullary blood flow and induces sodium retention and blood pressure elevation. Chronic medullary, but not intravenous, infusion of ACE inhibitor restores the impaired pressure natriuresis by improving medullary microcirculation in SHR. The tubuloglomerular feedback signal transmission is dependent on Cl concentration in the juxtaglomerular interstitium and its sensitivity is modulated by pressure there in.

Direct effects of angiotensin I, angiotensin II, an ACE inhibitor and a serine proteinase inhibitor on cultured heart cells from spontaneously hypertensive rats

1. The purpose of the present study was to investigate how angiotensin I (AI), angiotensin II (AII), an angiotensin converting enzyme inhibitor (ACE inhibitor; ACE-I) and a serine proteinase inhibitor contribute to the protein metabolism of cultured newborn spontaneously hypertensive rats (SHR) heart cells. We examined the uptake of [3H]-uridine and [3H]-proline into cultured cardiac myocytes and fibroblasts, respectively. 2. Both AI and AII increased the uptake of [3H]-uridine into myocytes in a concentration-dependent manner. However, the effect of AI was denied in the presence of the ACE-I with the concentration of 10(-6) g/mL. Both AI and AII increased the uptake of [3H]-proline into cardiac fibroblasts in a concentration-dependent manner. However, this effect was only partially abolished in the presence of 10(-6) g/mL of the ACE-I, which was the maximal concentration that did not exert any effect on the [3H]-proline uptake. In the presence of AII receptor antagonist, [Sar1, Leu8]-AII, the uptake of [3H]-proline into cardiac fibroblasts was completely inhibited. Moreover, the stimulatory effects of AI on the uptake of [3H]-proline into cardiac fibroblasts were completely inhibited in the presence of a serine proteinase inhibitor in addition to the ACE-I. 3. These results suggest that an ACE-I has different effects on protein metabolism in the heart and also suggest the presence of serine proteinase in cultured cardiac fibroblasts from SHR.

Contrasting effects of isoproterenol and phosphodiesterase III inhibitor on intracellular calcium transients in cardiac myocytes from failing hearts

1. Effects of a newly developed phosphodiesterase (PDE) III inhibitor, E-1020, on intracellular calcium transients were compared with those of isoproterenol (ISO) in isolated single myocytes from failing hearts secondary to pulmonary hypertension induced by monocrotaline injection. Myocytes were isolated by enzyme digestion using a Langendorff apparatus. Changes in intracellular calcium concentrations ([Ca2+]i) were recorded using a fura-2 fluorescence microscopic technique. Cyclic AMP contents of the hearts were measured by radio-immunoassay. 2. Myocytes from failing hearts showed Ca2+ transients with a low peak (low amplitude) and delayed decline of Ca2+ transients. Both ISO and E-1020 increased peak [Ca2+]i, max + d[Ca2+]i/dt, and max - d[Ca2+]i/dt in a concentration-dependent manner while both agents decreased T80L (time to 80% decline of amplitude from peak light). The concentrations which increased peak [Ca2+]i by 50% were 1.6 x 10(-9) mol/L of ISO and 2 x 10(-6) mol/L of E-1020. These concentrations increased cAMP in the heart to the same levels. Analysis of the effects of both agents on peak [Ca2+]i versus max - d[Ca2+]i/dt showed that ISO is much more effective on peak [Ca2+]i while E-1020 is more effective on max - d[Ca2+]i/dt. 3. These results showed that the effects of ISO and E-1020 on the parameters of intracellular Ca2+ transients of single myocytes from failing hearts are slightly different, and suggest that E-1020 may improve diastolic function as well as systolic function in failing hearts.

Renal effects of manidipine hydrochloride. A new calcium antagonist in hypertensive patients

The renal effects of manidipine hydrochloride were investigated in ten hospitalised patients with mild-to-moderate essential hypertension. After a one-week placebo period, manidipine was given for 1 week in a dose rising from 5 mg to 10 mg or 20 mg daily to normalise the mean blood pressure measured after 2 h. Blood pressure had decreased from 171/101 to 147/86 mm Hg at the end of manidipine treatment. The pulse rate was unaltered. Renal vascular resistance decreased from 1.90 to 1.33 dyn.s.cm-5/1.48 m2 x 10(4), and renal blood flow and glomerular filtration rate increased from 522 to 662 ml.min-1 x 1.48 m-2 and from 81 to 93 ml.min-1 x 1.48 m-2, respectively, in spite of a fall in renal perfusion pressure. Manidipine reduced the filtration fraction from 0.260 to 0.243, suggesting a preferential reduction in efferent arteriolar resistance. The fractional excretion of sodium and potassium did not change. Manidipine did not produce any significant alteration in plasma renin activity or in the plasma aldosterone concentration. The results indicate that manidipine has favourable renal effects and a concomitant hypotensive action in patients with mild-to-moderate essential hypertension.

[Evaluation of renal function using 99mTc-MAG3: comparison with 123I-OIH and 99mTc-DTPA]

The utility of 99mTc-mercaptoacetyltriglycine (MAG3) with studied clinically. In the renography obtained with 99mTc-MAG3, the abdominal aorta and the common iliac arteries were clearly visualized in the vascular phase. Due to less background activity and high target to background ratio, the quality of 99mTc-MAG3 image was superior to that of 123I-OIH or 99mTc-DTPA image. The parameters on the renogram including Tmax, T2/3, and T1/2 were compared. The correlation of Tmax and T2/3 or T1/2 were not significant between 99mTc-MAG3 and 123I-OIH. Another parameter of C20/Cmax, where C20 and Cmax are renal activities at 20 min after injection and at Tmax respectively, showed an excellent correlation between 99mTc-MAG3 and 123I-OIH. Using C20/Cmax, pattern of renogram can be characterized numerically. Concerning about the relation between C20/Cmax and renogram pattern, standard renogram pattern showed the C20/Cmax value of less than 0.4, while hypofunctioning pattern showed more than 0.5. The correlation coefficient between the renal uptake of 99mTc-MAG3 and 123I-OIH was 0.880 with a correlation plot: "Y = 1.16X-0.043", where X and Y represent renal uptake of 99mTc-MAG3 and 123I-OIH, respectively. It can be concluded that 99mTc-MAG3 is useful renal imaging agent as an alternative to 123I-OIH, in order to evaluate the proximal tubular function and calculate ERPF.

Effect of calcium antagonist, manidipine hydrochloride, on renal hemodynamics and tubuloglomerular feedback in spontaneously hypertensive rats

The effects of a calcium antagonist, manidipine, on renal hemodynamics and the tubuloglomerular feedback (TGF) mechanism were examined in 7- to 8-week-old spontaneously hypertensive rats (SHRs) and age-matched normotensive Wistar-Kyoto rats (WKYs). Manidipine, 10 micrograms/kg intravenously, reduced blood pressure only in SHRs. A greater increase in renal plasma flow occurred in SHRs, but effects on GFR were observed in both SHR and WKY rats. Filtration fraction decreased only in SHRs. The TGF response curve in SHRs was shifted to the left compared with that in WKY rats, indicating a more active TGF in hypertensive rats. Manidipine infusion produced a right and upward shift of the feedback curve in SHRs and only an upward shift in WKY rats. We conclude that manidipine corrects hyperactivity of the TGF mechanism in SHRs.

[Risk factors for contrast nephropathy in diabetic patients undergoing cardioangiography]

Risk factors for contrast nephropathy were prospectively studied in 17 patients with non-insulin dependent diabetes mellitus undergoing cardioangiography. Contrast nephropathy, defined as a serum creatinine increase of greater than 25% at 3 day after angiography, occurred in 29.4% of diabetic patients. Patients who developed contrast nephropathy had significantly higher serum creatinine (Cr), fractional excretion of sodium (FENa), urinary albumin excretion rate (AER), and lower 24hr Ccr than patients who did not (Cr: 1.5 +/- 0.3 mg/dl vs. 0.8 +/- 0.1 mg/dl, FENa: 1.9 +/- 0.5% vs. 0.6 +/- 0.1%, AER: 522 +/- 335 micrograms/min vs. 27 +/- 13 micrograms/min, 24hr Ccr: 39.1 +/- 11.6 ml/min vs. 86.2 +/- 9.3 ml/min, P < 0.05). Contrast nephropathy developed in all of two patients with overt proteinuria (AER more than 200 micrograms/min), but none of eight patients with normoalbuminuria (AER below 15 micrograms/min). Three of seven patients with microalbuminuria developed contrast nephropathy, and two of them had advanced nephropathy. FENa obtained next day was significantly elevated over baseline in patients with contrast nephropathy (1.9 +/- 0.5% vs. 9.7 +/- 4.5%, P < 0.05), but unchanged in patients without contrast nephropathy. The rise in C beta 2-microglobulin/Ccr and enzymuria was noted in both group. Percentage decrease of Ccr on the next day was positively correlated with FENa before angiography (r = 0.645, p < 0.01). Of 24hr Ccr, AER, and FENa before angiography, FENa was revealed as a statistically significant discriminant factor for contrast nephropathy by stepwise discriminant analysis (p = 0.0008). These results suggest that contrast nephropathy develops predominantly in the stage not of incipient but of overt diabetic nephropathy indicated by a decline of glomerular filtration, overt proteinuria, and tubular dysfunction. Of them, tubular dysfunction may be the most important risk factor for contrast nephropathy.

The use of purine-rich oligonucleotides in triplex-mediated DNA isolation and generation of unidirectional deletions

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[Renal adaptations to acid-base disorders]

Alterations in acid-base status affect renal hemodynamics and tubular function. GFR is reduced both in acute acidosis and alkalosis. Tubular functional adaptation to acute acidosis includes an acceleration in proximal acidification, induced by the increase in Pco2 and luminal bicarbonate concentration and a stimulated ammonia production, induced by low pH. Alteration in distal bicarbonate reabsorption is also an important determinant of the net acid excretion. Renal functional alterations in acute alkalosis include a reduction in GFR and a stimulated bicarbonate secretion in the cortical collecting duct. Proximal acidification is almost unchanged during acute alkalosis but reportedly accelerates after at least 3 weeks of maintained alkalosis. Renal adaptation during chronic phase of acid-base disorders differs from that during the acute phase.

Up-regulated MHC-class II expression and gamma-IFN and soluble IL-2R in lupus nephritis

Expression of MHC-class II molecules (HLA-DR and -DQ), serum gamma-interferon (gamma-IFN) and soluble interleukin-2 receptor (sIL-2R) levels were studied in 35 Japanese patients with lupus nephritis (LN) to clarify intraglomerular cellular activation and cytokine involvement in human LN. In 11 normal kidney specimens, HLA-DR(Ia1) was noted in glomerular tufts, but HLA-DQ was either not or was faintly detected in glomeruli by the indirect immunofluorescence technique. HLA-DR and -DQ were observed mainly on the surface of glomerular endothelial cells in 100% and 50% of 28 lupus kidney specimens except for necrotic or sclerotic lesions. HLA-DQ was expressed in a high incidence of 67%, 86% in patients with proliferative LN (WHO Class III-IV) and active lesions, respectively. Serum gamma-IFN and sIL-2R levels were 1.2 +/- 0.2 U/ml and 190 +/- 24 U/ml (mean +/- SEM; N = 30) in normal controls, and elevated in patients with proliferative LN (4.1 +/- 1.0 U/ml, 383 +/- 81 U/ml, N = 25), especially with active lesions (6.2 +/- 1.5 U/ml, 500 +/- 110 U/ml, N = 14). Overall, glomerular lesions such as HLA-DQ expression, the activity index and leukocyte infiltration correlated positively with serum gamma-IFN levels (r = 0.55; P less than 0.01 for HLA-DQ, r = 0.68; P less than 0.001 for activity index, r = 0.38; P less than 0.05 for leukocyte infiltration), but not with serum sIL-2R levels, anti-DNA antibody titers and CH50 titers.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of endothelin on renal hemodynamics and tubuloglomerular feedback

The effect of endothelin (ET)-1 infusion on renal hemodynamics and the tubuloglomerular feedback (TGF) mechanism was examined in rats. ET-1 reduced early proximal flow rate (EPFR) measured in the absence of distal flow from 28 +/- 1 to 23 +/- 1 nl/min at a subpressor dose (100 pmol.100 g body wt-1.h-1 iv) and from 27 +/- 2 to 19 +/- 2 nl/min at a pressor dose (200 pmol.100 g body wt-1.h-1). Reductions of EPFR induced by loop perfusion at 40 nl/min were 11 +/- 1 and 12 +/- 1 nl/min at the subpressor and pressor doses and were not different from controls. The stop-flow pressure response to loop perfusion was not altered by the pressor dose of ET-1. The subpressor dose of ET-1 increased renal vascular resistance (RVR) by 40% but left glomerular filtration rate (GFR) and urinary excretion of sodium (UNaV) unaltered. The pressor dose of ET-1 not only increased RVR by 140% and decreased GFR and renal plasma flow by 37 and 52%, but it increased UNaV proportional to the rise in blood pressure (r = 0.724, P less than 0.01). ET-1 is a potent renal vasoconstrictor and induces pressure natriuresis. ET-1 increases both pre- and postglomerular resistances but does not affect TGF response.

Bacteriostatic effect of 4,7-dicyanobenzofurazan due to inactivation of 2,3-dihydroxyisovalerate dehydratase

As part of our research on benzofurazans (BZs), we have reported the bacterioses of BZs in Escherichia coli, which may be due to O2-. produced within E. coli in the presence of dioxygen (O2). Incubation of E. coli with 4,7-dicyanobenzofurazan (1) lowered the 2,3-dihydroxyisovalerate dehydratase activity detectable in extracts from these cells. Addition of branched chain amino acids such as valine and leucine protected E. coli from growth inhibition by compound 1, though it could not protect E. coli from the damage by paraquat (PQ). Addition of Fe(III)-tris[N-(2-pyridylmethyl)-2-aminoethyl]amine (Fe-TPAA), a novel superoxide dismutase mimic, protected the dehydratase in a dose-dependent manner, which confirms that inactivation of the dehydratase is largely due to production of O2-.. The possibility was discussed that the bacteriostatic effect of compound 1 is due to the inactivation of 2,3-dihydroxyisovalerate dehydratase.

Renal effects of endogenous prostaglandin synthesis promoter ONO-3122

The renal effects of a prostaglandin synthesis agonist, 1-iodo-3-aminomethyl-5,6,7,8-tetrahydro-2-naphthol (ONO-3122), were investigated in anesthetized rats. ONO-3122 (0.3 mg/kg + 0.3 mg.kg-1.h-1 iv) doubled the urinary excretion of the main metabolites of prostaglandin F, and induced transient increases in renal blood flow and glomerular filtration rate (GFR) with a marked, stable natriuresis. Indomethacin suppressed the natriuresis. When the diuretic fluid losses were replaced, micropuncture showed an unaltered reabsorption of sodium in the proximal tubule but reductions in the loop of Henle (86 +/- 1 vs. 76 +/- 1%) and in the more distal segments (98 +/- 1 vs. 83 +/- 3%) with comparable reductions in water reabsorption. Potassium secretion was seen in the distal and collecting tubules. Without fluid replacement, sodium reabsorption was reduced in the loop and more distal nephron but increased in the proximal tubule. Differences between proximal and distal nephron GFR were unaffected by systemic ONO-3122. Loop perfusion with ONO-3122 did not change tubuloglomerular feedback responses, which were, however, completely suppressed by furosemide. It is concluded that ONO-3122 stimulates renal prostaglandin biosynthesis, transiently dilates renal vasculature, and induces natriuresis mainly by suppressing sodium and water reabsorption in the loop of Henle and the more distal nephron. Luminal ONO-3122 does not affect the tubuloglomerular feedback.