The orally active urotensin receptor antagonist, KR36676, attenuates cellular and cardiac hypertrophy.

BACKGROUND AND PURPOSE: Blockade of the actions of urotensin-II (U-II) mediated by the urotensin (UT) receptor should improve cardiac function and prevent cardiac remodelling in cardiovascular disease. Here, we have evaluated the pharmacological properties of the recently identified UT receptor antagonist, 2-(6,7-dichloro-3-oxo-2H-benzo[b][1,4]oxazin-4(3H)-yl)-N-methyl-N-(2-(pyrrolidin-1-yl)-1-(4-(thiophen-3-yl)phenyl) ethyl)acetamide (KR36676). EXPERIMENTAL APPROACH: Pharmacological properties of KR36676 were studied in a range of in vitro assays (receptor binding, calcium mobilization, stress fibre formation, cellular hypertrophy) and in vivo animal models such as cardiac hypertrophy induced by transverse aortic constriction (TAC) or myocardial infarction (MI). KEY RESULTS: KR36676 displayed high binding affinity for the UT receptor (Ki : 0.7 nM), similar to that of U-II (0.4 nM), and was a potent antagonist at that receptor (IC50 : 4.0 nM). U-II-induced stress fibre formation and cellular hypertrophy were significantly inhibited with low concentrations of KR36676 (≥0.01 µM). Oral administration of KR36676 (30 mg·kg(-1) ) in a TAC model in mice attenuated cardiac hypertrophy and myocardial fibrosis. Moreover, KR36676 restored cardiac function and myocyte size in rats with MI-induced cardiac hypertrophy. CONCLUSIONS AND IMPLICATIONS: A highly potent UT receptor antagonist exerted anti-hypertrophic effects not only in infarcted rat hearts but also in pressure-overloaded mouse hearts. KR36676 could be a valuable pharmacological tool in elucidating the complicated physiological role of U-II and UT receptors in cardiac hypertrophy.

Effect of curing time on the physicochemical and sensory properties of beef jerky replaced salt with soy sauce, red pepper paste and soybean paste.

This study was done to investigate the quality properties of beef jerky with soy sauce, red pepper paste, and soybean paste replacing salt. Sliced beef samples were cured in salt (control), soy sauce, red pepper paste, and soybean paste for 24 or 48 h and then dried at 70°C for 8 h. Treatments showed higher final moisture content and lower Na(+) concentration than the control after drying for 8 h. The lightness and shear force values were lower in all treatment samples than in the control during 48 h of curing time. In particular, lower lipid oxidation was found in the jerky cured with red pepper paste than in the control. Sensory evaluation showed that color, flavor, and tenderness of jerky samples were improved by replacing salt with soy sauce, red pepper paste and soybean paste, and higher likeability scores of the beef jerky were obtained among those treatments after 48 h of curing time.

Comparative virulence of reproductive diseases caused by type 1 (European-like) and type 2 (North American-like) porcine reproductive and respiratory syndrome virus in experimentally infected pregnant gilts.

The aim of this study was to compare the virulence of type 1 and type 2 porcine reproductive and respiratory syndrome virus (PRRSV) as assessed by the level of viral replication, viral distribution and apoptosis in stillborn fetuses and live-born piglets from infected pregnant gilts. Type 1 or type 2 PRRSV was given intranasally to pregnant gilts at 3 weeks before the expected date of parturition. Regardless of virus genotype, PRRSV-infected gilts farrowed between 102 and 109 days of gestation, while control uninfected gilts carried the pregnancy to term and farrowed at 114-115 days of gestation. There were no significant differences in the mean number of virus-infected cells per unit area of tissue when type 1 and type 2 virus infections were compared between stillborn fetuses and live-born piglets. Stillborn fetuses from the type 1 PRRSV-infected pregnant gilts had a significantly higher mean number of apoptotic cells per unit area of thymus (P = 0.013) than those from type 2 PRRSV-infected pregnant gilts. Significant differences in virulence were not observed between types 1 and 2 PRRSV in terms of female reproductive failure, although thymic apoptosis differed in stillborn fetuses from type 1 and type 2 PRRSV-infected pregnant gilts.

Comparative pathogenicity of three Korean and one Lelystad type 1 porcine reproductive and respiratory syndrome virus (pan-European subtype 1) isolates in experimentally infected pigs.

The aim of this study was to compare the pathogenicity of three type 1 porcine reproductive and respiratory syndrome virus (PRRSV) isolates that originated from Korean herds with varying severity of respiratory disease with one Lelystad virus. An experimental infection model was used to study virus distribution, sites of viral replication, viraemia, gross and microscopical lesions and the humoural immune response. Each virus isolate was given intranasally to 3-week-old pigs. Differences were found in the severity of gross and microscopical pulmonary lesions and the distribution of virus-labelled cells in lung and lymph nodes (LNs). The gross and microscopical pulmonary lesion scores were significantly greater in pigs inoculated with the SNUVR100744 isolate. The distribution of PRRSV-labelled cells within tissues and organs was similar for the different virus isolates; however, significantly more PRRSV-positive cells were detected in the lung and LNs of pigs inoculated with the SNUVR100744 isolate than were detected in the same tissues of pigs inoculated with Lelystad virus. The results of the present study demonstrate that type 1 PRRSV isolates differ in their ability to induce viral replication in tissues and induce interstitial pneumonia in pigs.

Pathogenesis of Korean type 1 (European genotype) porcine reproductive and respiratory syndrome virus in experimentally infected pregnant gilts.

The aims of this study were to determine (1) the pathogenesis of experimental infection with a Korean type 1 porcine reproductive and respiratory syndrome virus (PRRSV) by defining the viral distribution and the sites of viral replication and (2) the relationship between viral replication and apoptosis in stillborn fetuses and live born piglets from infected pregnant gilts. At 3 weeks ante partum, four pregnant gilts were inoculated intranasally with Korean type 1 PRRSV. Stillborn fetuses from the infected gilts were of crown-to-rump length 25.8-27.1 cm consistent with fetal death between 106 and 110 days of gestation. Type 1 PRRSV was isolated from the fetal tissues and these isolates were shown to be identical to the challenge virus by sequence analysis. Type 1 PRRSV RNA was detected in the lung, lymph node, heart, tonsil, thymus, liver, adrenal gland and spleen of live born piglets and stillborn fetuses from the infected gilts. The mean number of apoptotic cells per unit area of lung (P = 0.003), heart (P = 0.011), thymus (P = 0.003), liver (P = 0.011) and spleen (P = 0.002) was significantly higher in stillborn fetuses than in live born piglets. Dual labelling showed that the majority of cells either contained type 1 PRRSV or were apoptotic, but not both. Apoptotic cells were more numerous than PRRSV(+) cells. The results of the study demonstrated that type 1 PRRSV induces reproductive failure in pregnant gilts. Apoptosis induced by type 1 PRRSV may be associated with the incidence of stillborn fetuses in PRRSV-infected pregnant gilts.

Pathogenesis of type 1 (European genotype) porcine reproductive and respiratory syndrome virus in male gonads of infected boar.

The objective of this study was to determine the pathogenesis of experimental infection with a type 1 porcine reproductive and respiratory syndrome virus (PRRSV) by defining the sites of viral replication and apoptosis in male gonads from infected boars for a period of 21 days after intranasal inoculation. Microscopically, hypospermatogenesis and abundant germ cell depletion and death were observed in the testes. Such germ cell death occurs by apoptosis, as determined by a characteristic histological patterns and evidence of massive DNA fragment detected in situ terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end labeling (TUNEL) reaction. PRRSV was detected in the testicular tissue of infected boars only. Viral nucleic acid was localized in spermatogonia, spermatocytes and spermatids but not in the vesicular and bulbourethral gland. In serial sections, PRRSV-positive cells did not co-localized with apoptotic cells. TUNEL-positive apoptotic cells were more numerous than PRRSV-positive cells in testicular sections. The present study demonstrated that type 1 PRRSV infects the spermatogonia and their progeny, and induces apoptosis in these germ cells.

Expression of leucocyte function-associated antigen-1 and intercellular adhesion molecule-1 in the lungs of pigs infected with Actinobacillus pleuropneumoniae.

The aim of this study was to determine the expression of leucocyte function-associated antigen (LFA)-1 (CD11a/CD18) by neutrophils and intercellular adhesion molecule (ICAM)-1 (CD54) by endothelial cells in the lungs of pigs that had been infected experimentally with Actinobacillus pleuropneumoniae. Sixty-four 7-week-old conventional pigs were allocated randomly into infected (n = 40) or control (n = 24) groups. Five infected and three uninfected pigs were killed at 3, 6, 9, 12, 24, 36, 48 and 60 h post inoculation (hpi). Strong immunohistochemical expression of LFA-1 and ICAM-1 was detected frequently in neutrophils in the alveolar space and in endothelial cells in the capillaries of the alveolar septa, respectively. LFA-1 and ICAM-1 expression appeared to correlate with the onset of neutrophil infiltration into the alveolar space. The interaction between ICAM-1 and LFA-1 may be associated with the adherence of neutrophils to vascular endothelium, thereby permitting transmigration of these cells into inflamed lung.

Comparison of the virulence of European and North American genotypes of porcine reproductive and respiratory syndrome virus in experimentally infected pigs.

The objective of this study was to compare the virulence of Korean types 1 and 2 porcine reproductive and respiratory syndrome virus (PRRSV) isolated from weaned pigs with respiratory disease. Affected pigs were within the same herd and animals infected with type 2 virus had significantly higher mean rectal temperatures than those with type 1 virus between days 2 and 9 post-inoculation (P<0.05). Similarly, mean serum viral titres, expressed as tissue culture infective doses 50% (TCID50)/mL, as well as macroscopic and microscopic pulmonary lesion scores, were significantly higher at multiple time points in pigs infected with type 2 PRRSV compared to those infected with type 1 virus. Mean numbers of PRRSV-positive cells/unit area of lungs and lymph nodes were also significantly higher in type 2 PRRSV infected pigs. This study demonstrates that type 2 PRRSV is more virulent than type 1 PRRSV in this experimental setting as reflected by the pulmonary pathology induced, the extent of virus distribution, and oral shedding of the virus.

Gene pathways and cell cycle-related genes in cultured avian primordial germ cells.

Primordial germ cells (PGC) from early embryos are applicable to various kinds of research, including the production of transgenic animals. Primordial germ cells eventually migrate and differentiate into germ cells in the gonads, where they settle and rapidly proliferate. However, the proliferation rate of PGC is low in early embryos, and there are many significant pathways that mediate PGC activity. Therefore, in vitro culture of PGC from early embryos with efficient growth factors has been necessary. Recently, we cultured chicken PGC from embryonic d 2.5 with basic fibroblast growth factor and characterized the PGC through analysis of cell morphology, survival, proliferation, and apoptosis. However, large-scale analyses of genes expressed in cultured PGC and the genes involved in associated pathways are limited. The objective of the present investigation was to identify the signaling and metabolic pathways of expressed genes by microarray comparison between PGC and their somatic counterpart, chicken embryonic fibroblasts (CEF). We identified 795 genes that were expressed more predominantly in PGC and 824 genes that were expressed more predominantly in CEF. Among the predominant genes in PGC, 201 were differentially identified in 106 pathways. Among the predominant genes in CEF, 242 were differentially identified in 99 pathways. To further validate the genes involved in at least one candidate pathway, those involved in the cell cycle (12 predominant genes in PGC and 8 predominant genes in CEF) were examined by real-time PCR. To the best of our knowledge, this study is the first to investigate signaling and metabolic pathways in cultured PGC.

Conserved functional characteristics of the PIWI family members in chicken germ cell lineage.

The P-element-induced wimpy testis (PIWI) protein family, one of two subfamily members of Argonautes that regulate gene expression by associating with small noncoding RNAs, plays a role in maintaining the integrity of germ cells and stem cells. PIWI proteins have been identified and characterized in many species, including humans, mice, and zebrafish, but not as yet in avian species. In this study, chicken PIWI-like protein 1 (CIWI) and 2 (CILI) were identified from a 25-wk-old adult male testis cDNA library. Similar to mammals, CIWI and CILI have two conserved functional domains (PIWI/Argonaute/Zwille [PAZ] and PIWI), which bind the 3' end of single-stranded RNAs and the RNase H domain. The similarities between the PAZ and PIWI domain in CIWI were 65% and 80% to those of humans, and 67% and 80% to those of mice, respectively. In addition, the similarities between PAZ and PIWI in CILI were 60% and 61% to humans, and 60% and 63% to mice, respectively. Notably, the PIWI domain in the PIWIL1 protein showed high similarity between mammals and birds (80% between chickens and humans vs. 80% between chickens and mice), but the PIWI domain in PIWIL2 was less similar compared with PIWIL1 (61% between chickens and humans vs. 63% between chickens and mice). Reverse transcription polymerase chain reaction, quantitative real-time polymerase chain reaction, and in situ hybridization were conducted to analyze the expression patterns of PIWI family genes during gametogenesis in adult chickens during gonad development in the embryonic stage. CIWI and CILI showed germ cell-specific expression in both males and females, and CIWI and CILI mRNAs were distinctively expressed in different cell stages of spermatogenesis in testis. Using RNA interference, knockdowns of CIWI and CILI resulted in the increased expression of Chicken Repetitive 1 (CR1) Elements in primordial germ cells. Thus, the CIWI and CILI proteins of the PIWI family are conserved in avian species and play a critical role in germ line development and gametogenesis.

Pathogenesis of Korean type 1 (European genotype) porcine reproductive and respiratory syndrome virus in experimentally infected pigs.

The aim of this study was to elucidate the pathogenesis of experimental infection with Korean type 1 porcine reproductive and respiratory syndrome virus (PRRSV) by defining the virus distribution, sites of viral replication, viraemia and gross and microscopical lesions in conventional pigs studied for 28 days after intranasal inoculation. Mean rectal temperature was significantly higher in infected pigs than in negative control pigs at 2 days post inoculation (dpi) (P=0.004), 3 dpi (P<0.001), 4 dpi (P=0.003) and 5 dpi (P=0.034). The log(10)TCID(50)/ml of type 1 PRRSV increased significantly at 0-1 dpi (P=0.024) and 5-7 dpi (P=0.029), but decreased at 10-14 dpi (P=0.026) and 14-21 dpi (P=0.012) in infected pigs. Infected pigs developed multifocal, tan-mottled areas of lung tissue with irregular and indistinct borders. Microscopical lesions, when present, were multifocal, mild to moderate, generally most extensive at 5-7 dpi (P=0.036), and were nearly resolved at 28 dpi. Type 1 PRRSV nucleic acid and antigen were detected exclusively within the cytoplasm of macrophages and type I and II pneumocytes. The score for PRRSV-positive cells increased at 3-7 dpi (P<0.05) and decreased at 10-14 dpi (P=0.034) in infected pigs. Thus, respiratory disease was reproduced in conventional pigs by infection with Korean type 1 PRRSV.

Expression of secreted and membrane-bound mucins in the airways of piglets experimentally infected with Mycoplasma hyopneumoniae.

Immunohistochemistry was used to demonstrate secreted mucins MUC2, MUC5AC and MUC5B and membrane-bound mucin MUC4 in the pulmonary bronchioles of piglets experimentally infected with Mycoplasma hyopneumoniae. Conventional status, Landrace-Duroc cross-bred piglets, 13 days of age, were randomised to two groups. One group (n=20) was infected by the intra-tracheal route with the SNU98703 strain of M. hyopneumoniae, and a group of 12 animals acted as uninfected controls. Five infected and three uninfected piglets were euthanased on the day of infection and at 7, 21, and 35 days post-inoculation (PI). Membrane-bound MUC4 and secreted MUC5AC were the predominant mucins produced in the bronchioles of the piglets in response to M. hyopneumoniae infection, but by day 35 PI, all labelled mucins had returned to pre-infection levels, contemporaneous with reduced pulmonary lesion scores. The increased mucin production may result from direct stimulation of the epithelium by mycoplasmal infection, or may arise indirectly following M. hyopneumoniae-induced ciliostasis.

Comparative efficacy of commercial Mycoplasma hyopneumoniae and porcine circovirus 2 (PCV2) vaccines in pigs experimentally infected with M. hyopneumoniae and PCV2.

The efficacies of two commercial Mycoplasma hyopneumoniae bacterins and porcine circovirus 2 (PCV2) vaccines were compared in conventional pigs immunized at different ages based on humoral response, pathological observation, and growth performance from birth to finishing (175 days of age) using a M. hyopneumoniae and PCV2 co-infection challenge model. One-week-old pigs (n=110) were randomly assigned to five groups: three vaccinated and challenged (VC), and one each of non-vaccinated and challenged (NVC) and negative control. A significant difference was found in the number of genomic copies of M. hyopneumoniae in nasal swabs and PCV2 in serum samples, the average daily weight gain (gram/pig/day) between 63 and 133 dpi, gross and histopathological lung lesion scores, histopathological lymph node lesion scores, and the immunohistochemical analysis of PCV2 among the three VC groups. The single dose schedule for M. hyopneumoniae bacterins and PCV2 vaccines have the advantages of (i) improving daily weight gain (122.4%) and slaughter weight (120.5%), and (ii) reducing the incidence of clinical signs and lung and lymph node lesions.

Photoluminescence properties of non-tapered InN nanorods grown by plasma-assisted metalorganic chemical vapor phase deposition.

We have successfully grown non-tapered InN nanorods on Si substrate using an RF plasma assisted metalorganic chemical vapor deposition technique. Employment of 50 W nitrogen plasma reduces the optimal growth temperature to 500 degrees C. In order to study the temperature dependent bandgap and thermal quenching mechanism in relation to the localized states, photoluminescence measurement over a temperature range from 7 to 160 K are conducted. The photoluminescence at 7 K shows a strong near-band-emission energy of 0.682 eV with a narrow band width of 0.027 eV, which reveals excellent optical and structural qualities of the InN nanorods.

Hepatitis B virus X protein induces the expression of MTA1 and HDAC1, which enhances hypoxia signaling in hepatocellular carcinoma cells.

Expression level of metastasis-associated protein 1 (MTA1) is closely related to tumor growth and metastasis in various cancers. Although increased expression level of MTA1 was observed in hepatocellular carcinoma (HCC), role of MTA1 complex containing histone deacetylase (HDAC) in hepatitis B virus (HBV)-associated hepatocarcinogenesis has not been studied. Here, we demonstrated that HBx strongly induced the expression of MTA1 and HDAC1 genes at transcription level. MTA1 and HDAC1/2 physically associated with hypoxia-inducible factor-1 alpha (HIF-1 alpha) in vivo in the presence of HBx, which was abolished by knockdown of MTA1 by short interfering RNA (siRNA). HBx induced deacetylation of the oxygen-dependent degradation domain of HIF-1 alpha, which was accompanied with dissociation of prolyl hydroxylases and von Hippel-Lindau tumor suppressor from HIF-1 alpha. These results indicate that HBx-induced deacetylation is important for proteasomal degradation of HIF-1 alpha. Further, we observed that protein levels of MTA1 and HDAC1 were increased in the liver of HBx-transgenic mice. Also, there was a higher expression of HDAC1 in HCC than in the adjacent non-tumorous cirrhotic nodules in 10 out of 12 human HBV-associated HCC specimens. Together, our data indicate a positive cross talk between HBx and the MTA1/HDAC complex in stabilizing HIF-1 alpha, which may play a critical role in angiogenesis and metastasis of HBV-associated HCC.

A novel anti-ischemic ATP-sensitive potassium channel (K(ATP)) opener without vasorelaxation: N-(6-aminobenzopyranyl)-N'-benzyl-N' '-cyanoguanidine analogue.

This paper describes the design, synthesis, and biological evaluation of a novel anti-ischemic compound, (2S,3S,4R)-N-(6-amino-3,4-dihydro-2-dimethoxymethyl-3-hydroxy-2-methyl-2H-benzopyranyl)-N'-benzyl-N"-cyanoguanidine (33), and the structure-activity relationships leading to the discovery of this compound. Compound 33 significantly reduced the myocardial infarct zone to area at risk (IZ/AAR) in the ischemic myocardium rat model with high cardioselectivity. Since the cardioprotective effect of compound 33 is reversed by ATP-sensitive potassium channel (K(ATP)) blockers, its anti-ischemic effect appears to be at least mediated by K(ATP) opening. In addition, compound 33 shows good protective activity on neuronal cells against oxidative stress, and therefore it is suggested that compound 33 may have therapeutic potential both in cardio- and in neuroprotection.

Pharmacological characterization of KR-30988, a novel non-peptide AT1 receptor antagonist, in rat, rabbit and dog.

The pharmacological profile of KR-30988, a non-peptide AT1-selective angiotensin receptor antagonist, has been investigated by use of a variety of experimental models in-vitro and in-vivo. KR-30988 inhibited the specific binding of [125I][Sar1, Ile8]-angiotensin II to the recombinant AT1 receptor from man with a potency similar to that of losartan (IC50 values, the concentrations of drugs displacing 50% of specific binding, 13.6 and 12.3 nM, respectively), but did not inhibit the binding of [125I]CGP 42112A to recombinant AT2 receptor from man (IC50 >10 microM for both drugs). Scatchard analysis showed that KR-30988 interacted competitively with recombinant AT1 receptor from man in the same manner as losartan. In functional studies with rat and rabbit aorta, KR-30988 noncompetitively inhibited the contractile response to angiotensin II (pD2, = -log EC50 (where EC50 is the dose resulting in 50% of a reference contraction), 8.64 and 7.73, respectively) with a 20-85% decrease in the maximum contractile responses, unlike losartan. In pithed rats intravenous KR-30988 resulted in a non-parallel shift to the right of the dose-pressor response curve to angiotensin II (ID50 value, the dose inhibiting the pressor response to angiotensin II by 50%, 0.09 mg kg(-1)) with a dose-dependent reduction in the maximum responses; in this antagonistic effect KR-30988 was 20 times (approx.) more potent than losartan (ID50 1-74 mg kg(-1)). In conscious renal hypertensive rats oral administration of KR-30988 produced a dose-dependent and long-lasting (>24 h) anti-hypertensive effect; the potency was six times that of losartan (ED30 values, the dose reducing mean arterial blood pressure by 30 mmHg, 0.48 and 2.97 mg kg(-1), respectively). In conscious furosemide-treated dogs oral administration of KR-30988 produced a dose-dependent and long-lasting (>8 h) hypotensive effect with a rapid onset of action (time to Emax, the maximum effect, 1-2 h); KR-30988 was eight times more potent than losartan (ED20, the dose reducing mean arterial blood pressure by 20 mm Hg, 1.04 and 7.96 mg kg(-1), respectively). These results suggest that KR-30988 is a potent, orally active selective AT1 receptor antagonist with a mode of insurmountable antagonism.

In vivo pharmacologic profile of SK-1080, an orally active nonpeptide AT1-receptor antagonist.

The pharmacologic profile of SK-1080, a newly synthesized AT1-receptor antagonist, was evaluated in conscious normotensive rats, conscious renally (RHRs) and spontaneously (SHRs) hypertensive rats, and conscious furosemide-treated beagle dogs. In angiotensin II-challenged normotensive rats, orally administered SK-1080 had no agonistic effect and dose-dependently inhibited the pressor response to angiotensin II with a slightly weaker potency (ID50: 1.12 and 0.47 mg/kg, respectively), but with a more rapid onset of action than losartan (time to Emax, 30 min and 6 h, respectively). In RHRs, orally given SK-1080 produced a dose-dependent and long-lasting (>24 h) antihypertensive effect with a potency similar to that of losartan (ED20, 5.06 and 3.36 mg/kg, respectively). Intravenously administered SK-1080 exerted a very highly potent antihypertensive effect (ED20, 0.06 mg/kg), thus indicating a poor oral bioavailability in rats. On repeated dosing for 21 days in SHRs, SK-1080 significantly reduced blood pressure without inducing tachycardia and tolerance throughout the dosing period. On repeated dosing, the antihypertensive effect gradually increased from days 1 to 7 (Emax on day 7, 15.0 and 19.7% at 10 and 30 mg/kg, respectively) and remained at a significant level on days 14 and 21. In furosemide-treated dogs, orally given SK-1080 produced a dose-dependent and long-lasting (>8 h) antihypertensive effect with a rapid onset of action (time to Emax, 1-1.5 h) and 10-fold greater potency than losartan (ED20, 0.72 and 8.13 mg/kg, respectively). In furosemide-treated dogs, SK-1080 showed a good oral bioavailability, unlike that in RHRs. These results suggest that SK-1080 is a potent, orally active AT1-receptor antagonist useful for the treatment of hypertension.

Antihypertensive effects of the novel potassium channel activator SKP-450 and its major metabolites in rats.

Antihypertensive effects of SKP-450 (KR-30450, CAS 172489-10-0, (-)-(2R)-2"-(1",3"-dioxolan-2-yl)-2-2methyl-4-(2'-oxopyrr olidin-1-yl)-6- nitro-2H-1-benzopyran), a newly synthesized potassium channel activator, and its major metabolites SKP-818 ((-)-(2R)-2"-hydroxymethyl-2-methyl-4-(2'-oxopyrrolidin-1-yl)-6-ni tro- 2H-1-benzopyran) and SKP-310 ((-)-(2R)-2"-carboxy-2-methyl-4-(2'-oxopyrrolidin-1-yl)-6-nitro-2H -1- benzopyran) were evaluated in freely moving spontaneously hypertensive (SHR), renally hypertenisve (RHR), DOCA/salt-induced hypertensive (DHR) and normotensive rats (NR). The effects of long-term treatment with SKP-450 on blood pressure and arterial reactivity were also studied in SHR. SKP-450 (3-300 micrograms/kg, p.o.) and SKP-818 (3-100 micrograms/kg, i.v.) dose-dependently decreased mean arterial pressure (MAP) (potency order: SKP-450, RHR > SHR = DHR > NR; SKP-818, DHR = SHR = RHR > NR); however, SKP-310 did not influence MAP. Compared with lemakalim, SKP-450 was 2 to 5 fold more potent in SHR and NR, and equipotent in RHR and DHR. Repeatedly administration of SKP-450 to SHR over 21 days (10 and 30 micrograms/kg, p.o., once a day), had no significant effect on the degree and pattern of its antihypertensive effects and on the reactivity of isolated aorta to various vasoconstrictors and vasodilators. These results suggest that SKP-450 is a potent peripheral vasodilator acting without the development of tolerance and the alteration in vascular reactivity. SKP-818 and SKP-310 may play a role as an active metabolite and inactive intermediary, respectively.

Cardiovascular pharmacology of SKP-450, a new potassium channel activator, and its major metabolites SKP-818 and SKP-310.

The cardiovascular effects of SKP-450, a newly synthesized potassium channel activator, and its two major metabolites SKP-818 and SKP-310 were evaluated on isolated rat aorta and in freely moving rats and anesthetized beagle dogs. The rank order of potency in relaxing rat aorta precontracted with norepinephrine was SKP-450 > SKP-818 > Lemakalim > SKP-310 (EC50: 0.12, 0.55, 0.71 and 5.89 mumol/l, respectively). In rats, SKP-450, SKP-818 and lemakalim (3-100 micrograms/kg, i.v.) induced a dose-dependent decrease in mean arterial pressure (MAP; ED20: 9.8, 11.7 and 22.4 micrograms/kg, respectively) followed by reflex tachycardia. In dogs, SKP-818 and SKP-310 (0.3-1,000 micrograms/kg, i.v.) had quite similar hemodynamic profiles to SKP-450 but with a smaller potency. SKP-450, SKP-818 and SKP-310 dose-relatedly decreased MAP (ED20: 2.6, 4.2 and 588.8 micrograms/kg, respectively). They slightly increased left ventricular positive dP/dtmax with a transient decrease at the highest dose, while inducing a dose-related decrease in rate-pressure product, tension time index and systolic time. SKP-450, SKP-818 and SKP-310 induced a marked dose-dependent increase in coronary blood flow (Emax: 172.8, 257.9 and 178.7%, respectively) with less effects on blood flow through other arteries. Glybenclamide antagonized all the hemodynamic effects of SKP-450 in rats and dogs, whereas propranolol antagonized its reflex tachycardia in rats. These results indicate that SKP-450 is a potent coronary and peripheral vasodilator in rats and dogs activating ATP-sensitive potassium channels and that SKP-818 and SKP-310 exert a similar hemodynamic profile to the parent compound with equi- and weaker potency, respectively.