The in vitro pharmacological profile of KR31080, a nonpeptide AT1 receptor antagonist

Summary— KR31080 (2-butyl-5-methyl-6-(1-oxopyridin-2-yl)-3-[[2'-(1H-tetrazol-5-yl) biphenyl-4-yl]methyl]-3H-imidazo[4,5-b] pyridine) is a potent inhibitor of angiotensin type 1 (AT₁) receptors in rabbit aorta and human recombinant AT₁ receptors. In the isolated rabbit thoracic aorta, KR31080 caused a nonparallel shift to the right of the concentration-response curves to angiotensin II (All) with decreased maximal response (pD'₂ = 10.1 ± 0.1), but had no effect on the contractile response induced by norepinephrine. KR31080 inhibited specific [¹²⁵I]AII binding to rabbit aortic membranes (AT, receptors) and [¹²⁵I][Sar¹, Ile⁸]AII binding to human recombinant AT₁ receptors in a concentration-dependent manner with IC₅₀ values of 0.84 ± 0.08 nM and 1.92 ± 0.15 nM, respectively, but did not inhibit specific [¹²⁵I)AII binding to bovine cerebellum membranes (ÀT₂ receptors). In the Scatchard analysis, KR31080 interacted with rabbit aortic AT₁ receptors in a competitive manner, similar to losartan. These results demonstrate that KR31080 is a potent and AT₁ selective angiotensin receptor antagonist which exerts a competitive antagonism in the [¹²⁵I]AII binding assay and insurmountable AT₁ receptor antagonism in the functional study.     

A Chinese adolescent girl with Fechtner-like syndrome

We describe a 15-y-old girl with Fechtner-like syndrome, who is the first Chinese reported to have this rare syndrome. She presented with left homonymous hemianopia and neuroimaging revealed haemorrhage in both parietal and occipital lobes. Peripheral blood smear showed macrothrombocytopenia and intracytoplasmic inclusion bodies inside leucocytes. Thrombocytopenia and proteinuria responded to intravenous immunoglobulin and pulsed methylprednisolone. This case illustrates that life-threatening haemorrhage can occur in patients with Fechtner syndrome. Although there was no effective treatment reported in the literature, high dose steroid and immunoglobulin seemed to be useful in our patient. Our patient also had nephritic-nephrotic syndrome with renal insufficiency, which is unusual in adolescent female patients.     

Increase in survival time of liver transplants by protease inhibitors and a calcium channel blocker, nisoldipine

Kupffer cells are activated by calcium and release a variety of toxic mediators, including proteases. The purpose of these studies, therefore, was to determine if protease inhibitors and a calcium channel blocker could increase survival time in the rat model of orthotopic liver transplantation. Survival for 30 days was greater than 90% in this model when livers were stored for 1 hr in Ringer's solution (survival conditions)--however, grafts stored for 4 hr in Euro-Collins solution or 8 hr in University of Wisconsin (UW) solution survived postoperatively only 1.2 and 0.7 days, respectively (nonsurvival conditions). When livers were stored for 4 hr in Euro-Collins containing a cocktail of protease inhibitors (leupeptin, pepstatin A, phenylmethylsulfonyl fluoride, 20 ng/ml each; diisopropyl fluorophosphate, 100 microM) and subsequently transplanted, however, survival time was increased significantly to 11.5 days. Inclusion of a calcium channel blocker, nisoldipine (1.4 microM), in the protease inhibitor cocktail increased survival time to 23 days. Actually, nisoldipine alone increased survival time to 25 days. Nisoldipine alone also increased survival time in livers stored for 8 or 16 hr in UW solution to between 15 and 20 days. Serum transaminase levels reached peak values greater than 2400 U/L one day postoperatively in the nonsurvival groups, and liver injury assessed histologically was apparent. Under these conditions, pulmonary infiltration of inflammatory cells was observed in about 60% of the lungs examined and was associated with massive bleeding. Inclusion of the protease cocktail, nisoldipine, or both in the storage solutions decreased maximal SGOT levels and injury to both liver and lung significantly by about 50% postoperatively. Nisoldipine also decreased phagocytosis of carbon particles by the perfused liver 2- to 3-fold following storage under nonsurvival conditions (half-maximal effect = 0.3-0.4 microM nisoldipine). Moreover, nisoldipine improved hepatic microcirculation. It accelerated blood flow into the liver, as indexed by hemoglobin reflectance from the liver surface. These data support the hypothesis that Kupffer cells are activated early in the sequence of events that causes graft failure leading to endothelial cell-mediated alterations in the microcirculation. This work demonstrates clearly that dihydropyridine-type calcium channel blockers such as nisoldipine may be clinically useful in storage solutions for liver prior to transplantation.     

Evaluation of plantar hyperhidrosis in patients undergoing video-assisted thoracoscopic sympathectomy

Background Sympathectomy is the treatment of choice for primary hyperhidrosis. One curious occurrence that is difficult to explain from an anatomophysiological point of view in cases of video-assisted thoracoscopic sympathectomy (VATS) for the treatment of palmar hyperhidrosis (PH) is the observed improvement in plantar hyperhidrosis (PLH). Nevertheless, current reports on VATS rarely describe the effect on PLH or just give superficial data. The aim of this study was to prospectively investigate, how surgery affects PLH in patients with PH and PLH over one-year period. Methods From May 2003 to January 2004, 70 consecutive patients with combined PH and PLH underwent VATS at the T2, T3, or T4 ganglion level (47 women and 23 men, with mean age of 23 years). Results Immediately after the operation, all the patients said they were free from PH episodes, except for two patients (2.8%) who suffered from continued PH. Compensatory hyperhidrosis (CH) of various degrees was observed in 58 (90.6%) patients after one year. Only 13 (20.3%) suffered from severe CH. There was a great initial improvement in PLH in 50% of the cases, followed by progressive regression, such that only 23.4% still presented that improvement after one year. The number of cases without overall improvement increased progressively (from 17.1% to 37.5%) and the numbers with slight improvement remained stable (32.9–39.1%). Of the 24 patients with no improvement after one year, 6 patients graded plantar sweating worse. Conclusion Patients with PH and PLH who undergo VATS to treat their PH present a good initial improvement in PLH that reduces to a lower level of improvement after the one-year period.     

Mutagenicity of benzo(a)pyrenyl-1-sulfate in the Ames test.

Comparison of the mutagenicity of nine isomeric benzo(a)pyrenyl [B(a)P] phenols conjugated with either sulfate or glucuronide was carried out using strain Salmonella typhimurium TA98. Of the nine conjugates tested, only B(a)P-1-sulfate was mutagenic. Accordingly, the mutagenicity of B(a)P-1-sulfate was compared with that of B(a)P and 1-hydroxybenzo(a)pyrene [B(a)P-1-OH] in the presence and absence of rat lung S9 and Aroclor-induced liver S9 with and without an NADPH-generating system. B(a)P-1-sulfate was slightly mutagenic, whereas B(a)P and the 1-hydroxy derivative were nonmutagenic when S9 fractions and NADPH were omitted. Addition of induced liver S9 with NADPH caused mutagenicity with B(a) -1-OH greater than B(a)P greater than B(a)P-1-sulfate. B(a)P-1-sulfate was the only mutagenic species when lung S9 was added. This mutagenicity did not require NADPH. Sodium sulfite, an inhibitor of arylsulfatase, decreased the mutagenicity of B(a)P-1-sulfate. These data suggest that a unique mutagenic species is generated from B(a)P-1-sulfate via arylsulfatase in rat lung.     

Inhibition of glucuronidation of benzo(a)pyrene phenols by long-chain fatty acids

Long-chain fatty acids inhibit glucuronidation of benzo(a)pyrene phenols in perfused liver; therefore, this study was designed to investigate interactions of fatty acids with beta-glucuronidase, glucuronosyl transferase, and energy supply. In beta-glucuronidase-deficient C3H/He mice, infusion of oleate (250 microM) increased the release of free benzo(a)pyrene phenols from 14 to 33 nmol/g/h and decreased release of glucuronides into the perfusate from 25 to 17 nmol/g/h. Rates of accumulation of glucuronides in the liver were also diminished from 11 to 4 nmol/g/h after infusion of oleate (250 microM). Fatty acids did not affect the release of benzo(a)pyrene metabolites into bile, and the ratio of free phenol to glucuronide production was increased from 0.57 to 1.30. A similar trend was observed in livers from DBA/2 mice that have beta-glucuronidase. Rates of hydrolysis of benzo(a)pyrene-O-glucuronide were not altered in isolated microsomes by addition of oleoyl coenzyme A (CoA) or octanoyl CoA (10- approximately 100 microM). Thus, we conclude that fatty acids do not alter glucuronidation by acting on beta-glucuronidase. The concentration of cofactors (UDP-glucuronic acid, UDP-glucose, and adenine nucleotides) involved in hepatic conjugation was not altered by infusion of concentrations of oleate (300 microM) that inhibited glucuronidation in perfused livers. When oleate concentrations were increased to 600 microM, UDP-glucuronic acid and UDP-glucose decreased 44 and 49%, respectively, and the ATP:ADP ratio declined concomitantly. Oleoyl CoA inhibited UDP-glucuronosyl transferase noncompetitively (half-maximal inhibition, 10 microM) in microsomes with 3-hydroxy-benzo(a)pyrene or p-nitrophenol as substrate. In contrast, octanoyl CoA was a very poor inhibitor of transferase activity. Inhibition of the transferase by oleoyl CoA was increased markedly by treatment with detergents (Triton X-100), i.e., half-inhibition of glucuronosyl transferase was obtained with about 2 microM oleoyl CoA. Inhibition of UDP-glucuronosyl transferase by oleoyl CoA was also increased in a dose-dependent manner by albumin, possibly due to increasing access of the CoA derivative to the enzyme. Collectively, these data indicate that fatty acids diminish glucuronidation via the formation of acyl CoA compounds that inhibit UDP-glucuronosyl transferase noncompetitively.     

Conjugation of benzo(a)pyrene 7,8-dihydrodiol-9,10-epoxide in infant Swiss-Webster mice.

Benzo(a)pyrene 7,8-dihydrodiol-9,10-epoxide (BPDE), accepted as the ultimate carcinogen of benzo(a)pyrene, has a very short half-life in aqueous solutions yet induces lung tumors when injected into infant mice. To evaluate the possibility that metabolites of BPDE, principally in the form of stable conjugates, contribute to binding to DNA in peripheral tissues, infant mice were injected i.p. with 39 nmol (+/- ) anti-BPDE. One h after injection, 5% of the dose was recovered in serum and appeared mostly as conjugated metabolites (54% as glucuronides and 16% as glutathione conjugates). Amounts of direct acting electrophiles in serum estimated by trapping with DNA comprised less than 0.02% of the injected dose. No more than 10% of the radioactivity in extracts of liver, lung, and kidney was recovered as BPDE. Glutathione conjugates predominated in the liver and lung, whereas glucuronides were the major metabolites in kidney. Radioactivity bound to DNA in liver, lung, and kidney was 21.5, 42.7, and 7.8 pmol/mg, respectively. Despite the rapid conversion of BPDE to stable conjugates, 32P-postlabeling profiles of DNA adducts in lung closely resembled that noted after addition of BPDE directly to lung homogenate. Thus, the reactive intermediate as well as stable conjugates of BPDE may be transported to target tissues where they initiate tumors.     

Early diagnosis of acute postoperative renal transplant rejection by indium-111-labeled platelet scintigraphy

A prospective evaluation of 111In-labeled platelet scintigraphy (IPS) for the early diagnosis of acute postoperative renal transplant rejection (TR) was undertaken. The results of IPS were compared with in vitro biochemical tests, the clinical finding of graft tenderness, and combined [99mTc]DTPA and [131I]orthoiodohippurate scintigraphy. With a sensitivity of 0.93 and a specificity of 0.95, IPS provided otherwise unavailable diagnostic information. Furthermore, postoperative IPS was a good predictor of long-term allograft survival.