Microsatellite instability(MSI) in non-small cell lung cancer(NSCLC) is highly associated with transforming growth factor-beta type II receptor(TGF-beta RII) frameshift mutation

BACKGROUND

TGF-beta type II receptor (TGF-beta RII) mutations associated with microsatellite instability(MSI) are characteristically frameshift mutations within a 10 bp poly-A tract. These frameshift mutations have been reported to be common in colorectal and gastric cancers with MSI, though, rarely reported in non-small cell lung cancer (NSCLC).

MATERIALS AND METHOD

In this study, we analysed MSI and TGF-beta RII frameshift mutations in 7 NSCLC cell lines and 21 surgically resected NSCLC tissues. Determination of MSI in NSCLC was performed using primer sets for BAT-25, BAT-26 and BAT-40. In order to examine the presence of the frameshift mutations of TGF-beta RII in samples with MSI, sequencing for TGF-beta RII poly-A tract was performed.

RESULTS

MSI was observed in 5 out of 7 NSCLC cell lines and 3 out of 21 NSCLC tissues. Six out of 8 samples with MSI(75%) showed frameshift mutations in TGF-beta RII poly-A tract.

CONCLUSION

These results suggest that MSI is highly associated with TGF-beta RII frameshift mutations in NSCLC and further support the hypothesis that TGF-beta RII plays an important role in NSCLC carcinogenesis.

Percutaneous gallbladder drainage for delayed laparoscopic cholecystectomy in patients with acute cholecystitis

BACKGROUND

Many studies have concluded that delayed or interval laparoscopic cholecystectomy (LC) in patients with acute cholecystitis (AC) demonstrated higher conversion rates and complication rates compared with early LC. However, if the acutely inflamed gallbladder is decompressed by emergent percutaneous gallbladder drainage (PGBD), it may decrease the technical difficulty of LC allowing successful delayed LC when the patient is in better condition. The purpose of this retrospective study was to assess the outcomes of delayed LC following PGBD in patients with AC.

METHODS

A total of 72 LC for AC were divided into PGBD (n = 27) and non-PGBD groups (n = 45). The PGBD group had delayed LC (after 72 hours of admission). Thirty-two non-PGBD patients had early LC (within 72 hours of admission) and 13 non-PGBD had delayed LC. Outcome of delayed LC for the PGBD group was assessed by LC time, conversion rate, morbidity rate, and hospital stay, and compared with that of the non-PGBD group.

RESULTS

Compared with early and delayed LC of the non-PGBD group, the PGBD group showed longer LC time (median 110 minutes versus 87.5 minutes versus 85 minutes, P <0. 05), a little lower conversion rate (15% versus 25% versus 23%), similar morbidity rate (15% versus 9% versus 15%), and prolonged hospital stay (13 days versus 7 days versus 10 days).

CONCLUSIONS

PGBD did not significantly improve the outcome of LC for AC as assessed by conversion and morbidity rate and hospital stay compared with no PGBD. Thus, we can conclude that although PGBD is a safe and effective emergency procedure for AC, it should be limited to higher risk groups such as elderly or critically ill patients and to acalculous cholecystitis.

Biliary metabolites of beta-artemether in rats: biotransformations of an antimalarial endoperoxide

beta-Artemether (AM), the O-methyl ether prodrug of dihydroartemisinin (DHA), is an endoperoxide antimalarial. The biliary metabolites of AM in adult male Wistar rats were characterized with particular reference to potential antimalarial compounds and stable derivatives of free radical intermediates. [13-(14)C]-AM (35 micromol kg(-1), i.v.) was administered to anesthetized rats. Within 0 to 3 h, 38.6 +/- 4.8% (mean +/- S.D., n = 6) of the radiolabel was recovered in bile; the 0- to 5-h recovery was 42.3 +/- 4.3%. The major metabolites (0-3 h) were the glucuronides of 9alpha-hydroxyAM (33.4 +/- 6.8% biliary radioactivity) and alpha-DHA (22.5 +/- 4.4%); four stereochemically unassigned monohydroxyAM glucuronides (II, 3.1 +/- 0.9; IV, 4.4 +/- 1.7%; V, 21.4 +/- 3.0%; VI, 3.0 +/- 1.1%) and a dihydroxyAM glucuronide (6.0 +/- 2.1%) were also identified. A sixth monohydroxyAM glucuronide (VIIa) and desoxyDHA glucuronide were detected in trace amounts. The furano acetate isomer of DHA glucuronide, indicative of the formation of a radical intermediate, was also found in trace amounts. O-methyl substitution of DHA favors ring hydroxylation in vivo. However, the principal hydroxylated metabolite, 9alpha-hydroxyAM, is unlikely to possess significant antimalarial activity.

A highly conserved enhancer in the Dlx5/Dlx6 intergenic region is the site of cross-regulatory interactions between Dlx genes in the embryonic forebrain

Four Dlx homeobox genes, Dlx1, Dlx2, Dlx5, and Dlx6 are expressed in the same primordia of the mouse forebrain with temporally overlapping patterns. The four genes are organized as two tail-to-tail pairs, Dlx1/Dlx2 and Dlx5/Dlx6, a genomic arrangement conserved in distantly related vertebrates like zebrafish. The Dlx5/Dlx6 intergenic region contains two sequences of a few hundred base pairs, remarkably well conserved between mouse and zebrafish. Reporter transgenes containing these two sequences are expressed in the forebrain of transgenic mice and zebrafish with patterns highly similar to endogenous Dlx5 and Dlx6 expression. The activity of the transgene is drastically reduced in mouse mutants lacking both Dlx1 and Dlx2, consistent with the decrease in endogenous Dlx5 and Dlx6 expression. These results suggest that cross-regulation by Dlx proteins, mediated by the intergenic sequences, is essential for Dlx5 and Dlx6 expression in the forebrain. This hypothesis is supported by cotransfection and DNA-protein binding experiments. We propose that the Dlx genes are part of a highly conserved developmental pathway that regulates forebrain development.

Somatostatin and substance P induced in vivo by lipopolysaccharide and in peritoneal macrophages stimulated with lipopolysaccharide or interferon-gamma have differential effects on murine cytokine production

We have investigated whether lipopolysaccharide (LPS) induces substance P (SP) and somatostatin (SOM) in popliteal lymph nodes in vivo and whether macrophages are a source of SP and SOM in vitro. We have also investigated the effect of SP and SOM treatment on the production of cytokines. SP reached a maximum 3 days after injection of LPS (100 microg/footpad) and then declined. SOM expression after LPS injection reached a maximum at 5-7 days. Stimulation of thioglycolate-elicited peritoneal macrophages with LPS (20 microg/ml), recombinant interferon-gamma (rIFN-gamma, 100 U/ml), and LPS plus rIFN-gamma induced SOM and SP. Thioglycolate-elicited, unstimulated peritoneal macrophages also synthesized these peptides. SOM (10(-12)-10(-8) M) significantly inhibited IL-6 and IFN-gamma production, whereas SP at those concentrations enhanced cytokine production by activated lymphocytes and macrophages. These findings suggest that neuropeptides which originate from macrophages and nerve fibers act as immunomodulators to mediate changes in the pattern of cytokine production.

Novel, potent, semisynthetic antimalarial carba analogues of the first-generation 1,2,4-trioxane artemether

Ten novel, second-generation, fluorinated ether and ester analogues of the potent first-generation analogues artemether (4a) and arteether (4b) have been designed and synthesized. All of the compounds demonstrate high antimalarial potency in vitro against the chloroquine-sensitive HB3 and -resistant K1 strains of Plasmodium falciparum. The most potent derivative 8 was 15 times more potent than artemisinin (2) against the HB3 strain of P. falciparum. In vivo, versus Plasmodium berghei in the mouse, selected derivatives were generally less potent than dihydroartemisinin with ED(50) values of between 5 and 8 mg/kg. On the basis of the products obtained from the in vitro biomimetic Fe(II)-mediated decomposition of 8, the radical mediator of biological activity of this series may be different from that of the parent drug, artemisinin (2).

Collision tumors of the ovary associated with teratoma: clues to the correct preoperative diagnosis

PURPOSE

Collision tumors represent a coexistence of two adjacent but histologically distinct tumors without histologic admixture in an organ. The purpose of this study was to describe the imaging findings of collision tumors of the ovary associated with teratoma and to look for clues that might lead to the correct preoperative diagnosis.

METHOD

Seven pathologically proven cases of collision tumor of the ovary associated with teratoma were retrospectively reviewed. Ovarian teratomas were coexistent with mucinous cystadenoma (n = 4), borderline mucinous tumor (n = 1), mucinous cystadenocarcinoma (n = 1), and dysgerminoma (n = 1). US (n = 5), CT (n = 3), and/or MRI (n = 4) findings were evaluated.

RESULTS

In addition to the typical findings of teratoma, the mass contained a multiloculated cystic portion filled with nonfatty fluid, suggesting the coexistent epithelial tumor in five cases. In one case, the mass contained a large solid component, suggesting the possibility of collision tumor. In the remaining one case, coexistent small mucinous cystadenoma could not be identified.

CONCLUSION

Preoperative imaging for ovarian teratoma revealed a collision tumor in six of seven cases. The possibility of a collision tumor should be considered when an ovarian teratoma has imaging findings that cannot be explained solely by an ovarian teratoma.

New 4-aminoquinoline Mannich base antimalarials. 1. Effect of an alkyl substituent in the 5'-position of the 4'-hydroxyanilino side chain

A new series of 4-aminoquinoline Mannich base derivatives have been synthesized, in which the 3'-diethylamino function of amodiaquine (AQ) is replaced by a 3'-tert-butylamino group and an aliphatic hydrocarbon entity is incorporated into the 5'-position of the 4'-hydroxyanilino side chain. Seven alkyl Mannich base derivatives were screened and found to be active against both chloroquine-sensitive and -resistant strains of Plasmodium falciparum in vitro. The propyl and isopropyl alkyl derivatives were found to be the most active; consequently these derivatives were tested against a nonsensitive strain of Plasmodium berghi in vivo and found to be 3-fold more active than AQ, irrespective of the route of administration (oral or intraperitoneal).

The adverse effects of drugs

Adverse drug reactions vary in presentation and severity, and can mimic almost any disease. The article explores the importance of adverse drug reactions in modern clinical practice, highlighting the mechanisms and how to manage patients.

Metabolism of the antimalarial endoperoxide Ro 42-1611 (arteflene) in the rat: evidence for endoperoxide bioactivation

Ro 42-1611 (arteflene) is a synthetic endoperoxide antimalarial. The antimalarial activity of endoperoxides is attributed to iron(II)-mediated generation of carbon-centered radicals. An alpha, beta-unsaturated ketone (enone; 4-[2',4' bis(trifluoromethyl)phenyl]-3-buten-2-one), obtained from arteflene by reaction with iron(II), was identified previously as the stable product of a reaction that, by inference, also yields a cyclohexyl radical. The activation of arteflene in vivo has been characterized with particular reference to enone formation. [14C]Arteflene (35 micromol/kg) was given i.v. to anesthetized and cannulated male rats: 42.2 +/- 7.0% (mean +/- S.D., n = 7) of the radiolabel was recovered in bile over 5 h. In the majority of rats, the principal biliary metabolites were 8-hydroxyarteflene glucuronide (14.2 +/- 3. 9% dose, 0-3 h) and the cis and trans isomers of the enone (13.5 +/- 4.6% dose, 0-3 h). In conscious rats, 15.3 +/- 1.6% (mean +/- S.D., n = 8) of the radiolabel was recovered in urine over 24 h. The principal urinary metabolite appeared to be a glycine conjugate of a derivative of the enone. Biliary excretion of the glucuronide, but not of the enones, was inhibited by ketoconazole. 8-Hydroxyarteflene was formed extensively by rat and human liver microsomes but no enone was found. Bioactivation is a major pathway of arteflene's metabolism in the rat. Although the mechanism of in vivo bioactivation is unclear, the reaction is not catalyzed by microsomal cytochrome P-450 enzymes.

The effect of genetic polymorphisms in CYP2C9 on sulphamethoxazole N-hydroxylation

Sulphamethoxazole undergoes CYP2C9-mediated bioactivation to a hydroxylamine. In this study, we investigated the effect of the CYP2C9Arg144 to Cys (CYP2C9*2) and CYP2C9Ile359 to Leu (CYP2C9*3) polymorphisms on sulphamethoxazole N-hydroxylation. Human livers were genotyped using polymerase chain reaction amplification and restriction fragment length polymorphism analysis. Formation of sulphamethoxazole hydroxylamine and methylhydroxy tolbutamide in microsomes prepared from cell lines and the genotyped human livers was determined by high-pressure liquid chromatography. Microsomes prepared from the cell line expressing the allelic variants CYP2C9-Cys144 and CYP2C9-Leu359 displayed a threefold and 20-fold decrease in intrinsic clearance (Cl(int)) for sulphamethoxazole, respectively, when compared with the wild-type, CYP2C9-Arg144. A significant decrease (P < 0.05) in Cl(int) was also observed with tolbutamide for both mutations. Of the 26 human livers genotyped, 61.5% were homozygous wild-type, 26.9% were heterozygotes for CYP2C9*2 and 15.4% were heterozygotes for CYP2C9*3. No homozygous mutant livers were detected. There was a good correlation between sulphamethoxazole N-hydroxylation and tolbutamide methyl hydroxylation (r = 0.825). However, there was no difference in the kinetic parameters for either sulphamethoxazole N-hydroxylation or tolbutamide methyl hydroxylation between the wild type livers (n = 6) and either the livers heterozygous for the CYP2C9*2 (n = 5) or the livers heterozygous for the CYP2C9*3 mutation (n = 3). The CYP2C9*2 and CYP2C9*3 polymorphisms may have some influence on the bioactivation of sulphamethoxazole, particularly in individuals who are homozygous mutants, and this could act as a protective factor against sulphamethoxazole hypersensitivity. However, given the rarity of homozygous mutants, it is likely that other metabolic and immunological risk factors will dominate individual susceptibility.

Alpha-hydroxytamoxifen, a genotoxic metabolite of tamoxifen in the rat: identification and quantification in vivo and in vitro

The metabolic formation of a-hydroxytamoxifen, a reactive metabolite of tamoxifen in rat liver, was characterized and quantified in vitro (hepatic microsomal incubations) and in vivo (bile-duct cannulated animals). This minor metabolite was identified by chromatographic and mass spectral comparisons with the authentic compound. The rates of formation of alpha-hydroxytamoxifen in incubations (30 min) of tamoxifen (25 microM) with liver microsomal preparations from women (pool of six), female CD1 mice or female Sprague-Dawley rats, as quantified by liquid chromatography-mass spectrometry (LC-MS), were 1.15+/-0.03, 0.30+/-0.05 and 2.70+/-0.35 pmol/min/mg protein, respectively. Selective inhibition of microsomal P450 indicated that alpha-hydroxylation was catalysed predominantly by CYP3A in humans. Bile-duct cannulated and anaesthetized female rats and mice given [14C]tamoxifen (43 micromol/kg, i.v.) excreted, respectively, 24 and 21% of the administered radioactivity in bile over 5 and 3.5 h. The major radiolabelled biliary metabolite in rats, characterized by LC-MS after enzymic hydrolysis of conjugates, was the glucuronide of 4-hydroxytamoxifen (10% of dose) and only 0.1% of the dose was recovered as alpha-hydroxytamoxifen. After administration of alpha-hydroxytamoxifen (43 micromol/kg, i.v.) to rats, only 1.19% of the administered compound was recovered from a glucuronide metabolite in bile, indicating a possible 0.84% alpha-hydroxylation of tamoxifen in vivo. There was, however, no indication of the presence in bile of either O-sulphonate or glutathione conjugates derived from alpha-hydroxytamoxifen. This study shows for the first time that alpha-hydroxytamoxifen can be glucuronylated in rat liver. Whereas sulphonation results in electrophilic genotoxic intermediates, glucuronidation may represent a means of detoxifying alpha-hydroxytamoxifen.

Metabolism-dependent neutrophil cytotoxicity of amodiaquine: A comparison with pyronaridine and related antimalarial drugs

Life-threatening agranulocytosis and hepatotoxicity during prophylactic administration of amodiaquine have led to its withdrawal. Agranulocytosis is thought to involve bioactivation to a protein-reactive quinoneimine metabolite. The toxicity of amodiaquine and the lack of cheap drugs have prompted a search for alternative antimalarial agents. The aim of this study was to determine the metabolism and neutrophil toxicity of amodiaquine, pyronaridine, and other related antimalarial agents. Horseradish peroxidase and hydrogen peroxide were used to activate drugs to their respective quinoneimine metabolites. Metabolites were trapped as stable glutathione conjugates, prior to analysis by LC/MS. Amodiaquine was metabolized to a polar metabolite (m/z 661), identified as a glutathione adduct. Tebuquine was converted to two polar metabolites. The principal metabolite (m/z 686) was derived from glutathione conjugation and side chain elimination, while the minor metabolite gave a protonated molecule (m/z 496). Only parent ions were identified when chloroquine, cycloquine, or pyronaridine was incubated with the activating system and glutathione. Calculation of the heat of formation of the drugs, however, demonstrated that amodiaquine, tebuquine, cycloquine, and pyronaridine readily undergo oxidation to their quinoneimine. None of the antimalarial compounds depleted the level of intracellular glutathione (1-300 microM) when incubated with neutrophils alone. Additionally, with the exception of tebuquine, no cytotoxicity below 100 microM was observed. In the presence of the full activating system, however, all compounds except chloroquine resulted in depletion of the level of glutathione and were cytotoxic. Pretreating the cells with glutathione and other antioxidants inhibited metabolism-dependent cytotoxicity. In summary, our data show that amodiaquine and related antimalarials containing a p-aminophenol moiety undergo bioactivation in vitro to chemically reactive and cytotoxic intermediates. In particular, pyronaridine, which is currently being investigated in humans, was metabolized to a compound which was toxic to neutrophils. Thus, the possibility that it will cause agranulocytosis in clinical practice cannot be excluded, and will require careful monitoring.

Expression of cytochrome P4502E1 in human liver: assessment by mRNA, genotype and phenotype

Cytochrome P4502E1 (CYP2E1) is constitutively expressed in human liver and is responsible for the metabolic bioactivation of a wide variety of xenobiotics, including a number of protoxins and procarcinogens. CYP2E1 expression is regulated at several levels including pre-transcriptional, transcriptional and post-transcriptional levels, and any variation in enzyme concentration and hence activity may represent increased risk of toxicity or carcinogenicity. We have investigated variability in the levels of CYP2E1 mRNA, protein and functional activity in a human liver bank, and attempted to relate these parameters to the RsaI restriction fragment length polymorphism in the 5'-flanking region. Variation in CYP2E1 mRNA (18-fold) was greater than the variation seen in CYP2E1 protein (twofold) and functional activity (fourfold) determined using two probe substrates, chlorzoxazone and p-nitrophenol. Although protein and functional activity showed a significant correlation (r = 0.93 and r = 0.83 for chlorzoxazone and p-nitrophenol, respectively), there was no correlation between any of these parameters and mRNA levels. Also, the variation in CYP2E1 activity could not be directly accounted for by the RsaI polymorphism in our samples. In conclusion, our results are consistent with a complex regulation of CYP2E1 and the fact that it is highly conserved in the human population. The absence of a relationship between the RsaI polymorphism and CYP2E1 activity is consistent with other studies performed in Caucasians, but does not exclude an effect of this polymorphism on inducibility of CYP2E1.

Assessment of the effect of malaria infection on hepatic clearance of dihydroartemisinin using rat liver perfusions and microsomes

1. The clearance of dihydroartemisinin (DHA) in control and malaria-infected (MI) rats was investigated using the isolated perfused rat liver (IPRL) model and hepatic microsomal studies. 2. In the recirculating IPRL, clearance of DHA was reduced from a mean (s.d.) of 8.2+/-1.8 ml min(-1) in controls (n=8) to 6.0+/-1.0 ml min(-1) in MI (n=8; P<0.01). Clearance in control livers was similar to the perfusion flow rate, suggesting a high hepatic extraction ratio for DHA. 3. Single-pass IPRL studies in controls (n=8) showed that DHA bioavailability at 1.3, 8 and 38 microm was 0.026+/-0.020, 0.043+/-0.025 and 0.14+/-0.06, respectively (P<0.001 for 8 microM vs 38 microM). In MI livers (n=5), DHA bioavailability at 8 and 38 microM was 0.18+/-0.07 and 0.40+/-0.08, respectively (P=0.002). Bioavailability was higher in the MI group than in controls (P=0.01 at 8 microM and P<0.001 at 38 microM). DHA-glucuronide was the sole biliary metabolite. 4. Hepatic microsomal studies of DHA-glucuronide formation showed a significantly lower Vmax but no significant change in Km, in MI compared to control livers (n=6). Intrinsic metabolic clearance (Vmax/Km) was higher in control than in MI livers (5.2+/-1.3 and 2.5+/-1.4 microl min(-1) mg(-1), respectively; P=0.006). 5. These studies demonstrate that DHA has a high, concentration-dependent hepatic extraction ratio that is reduced by 20-30% in the P. berghei rodent malaria model. The impaired hepatic clearance of DHA in MI is attributable to a reduction in intrinsic metabolic clearance.

Effect of disposition of mannich antimalarial agents on their pharmacology and toxicology

The use of the antimalarial agent amodiaquine has been curtailed due to drug-induced idiosyncratic reactions. These have been attributed to the formation of a protein-reactive quinoneimine species via oxidation of the 4-aminophenol group. Therefore, the effects of chemical modifications on the disposition of amodiaquine in relation to its metabolism, distribution, and pharmacological activity have been investigated. The inclusion of a group at the C-5' position of amodiaquine reduced or eliminated bioactivation, as determined by glutathione conjugate formation in vivo. This can be seen in two series of C-5'-substituted compounds: the bis-Mannich antimalarial agents, including cycloquine and pyronaridine, and mono-Mannich antimalarial agents containing a 5'-chlorophenyl group (tebuquine and 5'-ClPAQ). Chemical substitution at the C-5' position also resulted in compounds which underwent slower elimination (<5% of the dose excreted into bile and urine, compared with 50% for amodiaquine) and increased levels of accumulation in tissue (10% of the dose in the liver at 48 h compared with 1% with amodiaquine). This may be due to an increase in either the lipophilicity or the basicity of the analogs and may reflect the lack of metabolic clearance for these compounds. The alteration in the disposition following the introduction of the C-5' substituent resulted in an increased duration of antimalarial activity in the mouse compared with that for amodiaquine. While this is desirable in the treatment of malaria, repeated administration for prophylaxis may induce toxicity through accumulation. Therefore, by simple chemical modification it is possible to block the bioactivation of amodiaquine while maintaining and in some cases extending the duration of antimalarial activity.

The role of iron in neurotoxicity: a study of novel antimalarial drugs

The antimalarial drug artemisinin and its derivatives display neurotoxicity in animal studies in vivo and in neuronal cells in vitro. Their toxicity may be due to an interaction of iron with the endoperoxide bridge of the derivative to produce toxic free radicals and/or other toxic metabolites. In this study, 0.3 microM artemether (AEM) in the presence of 2 microM haemin significantly inhibited the outgrowth of neurites from differentiating NB2a neuroblastoma cells by up to 76%. The antioxidants ascorbic acid and glutathione completely protected against this toxicity at a concentration of 100 microM. AEM was found to be partially converted to two isomeric products, which were identified as the tetrahydrofuran acetate isomer of AEM and 3alpha-hydroxydesoxyartemether.

Localization of atrial natriuretic peptide receptors in the rat tongue and hard palate

Atrial natriuretic peptide (ANP) receptors were characterized in rat oral mucosa using quantitative in vitro autoradiography and activation of particulate guanylyl cyclase (GC) by natriuretic peptides. Competition-binding analysis performed by quantitative in vitro autoradiography demonstrated specific [125I]rANP(1-28) binding sites in the tongue and hard palate. The precise location of this binding was revealed on the basal and parabasal cells of the epithelia by microautoradiography. The dissociation constant (Kd) and maximal binding capacity (Bmax) of these sites were 3.34+/-1.35 nM and 2.71+/-2.21 fmol/mm2 on the epithelium of the tongue, and 4.09+/-1.52 nM and 3.45+/-3.01 fmol/mm2 on the epithelium of the hard palate, respectively. Receptor subtypes were characterized by competition with des [Gln18, Ser19, Gly20, Leu21, Gly22] ANP(4-23) (C-ANP), a specific ligand for the clearance receptor (NPR-C). These binding sites were displaced by C-ANP with inhibition constant (Ki) of 8.96+/-3.18 nM and Bmax of 2.89+/-2.45 fmol/mm2 on the epithelium of the tongue, and Ki of 9.12+/-2.71 nM and Bmax of 3.08+/-2.94 fmol/mm2 on the epithelium of the hard palate, respectively. Production of cyclic GMP by particulate GC in the epithelial membranes of the tongue and hard palate was stimulated by rANP(1-28), porcine brain natriuretic peptide (BNP)(1-26), and C-type natriuretic peptide (CNP)(1-22) in a dose-dependent manner. These results indicate that ANP-binding sites in the epithelium of the tongue and hard palate are mainly clearance receptors (NPR-C) but biological receptors (NPR-A and/or NPR-B) with GC activity are also present, and suggest that ANP may have a role in the proliferation of the oral epithelial cells, especially in the tongue and hard palate.