Absorption, metabolism and excretion after oral administration of a new Ca antagonist, 14C-benidipine hydrochloride to man

1. In healthy male volunteers, the absorption, metabolite profiles and excretion of 14C-benidipine hydrochloride, a new Ca antagonist, were investigated after oral administration at a dose of 8 mg. 2. 14C-benidipine hydrochloride was rapidly absorbed, and the plasma concentration of radioactivity and unchanged drug reached a maximum of 71.2 ng eq./ml at 1.1 h and 2.56 ng/ml at 0.6 h respectively, and then declined bi-exponentially. The half-life in the elimination phase was 14.7 and 5.3 h respectively, AUC of unchanged drug was low, about 1% of that of radioactivity. 3. Five days after administration, 36.4% of the administered radioactivity was excreted in urine and 58.9% in faeces. 4. The metabolite profiles in plasma, urine and faeces were analysed by hplc. At 1 h after administration the predominant metabolites in plasma were M9 and M2, which accounted for 13.8 and 8.2% of the radioactivity respectively, whereas unchanged drug represented 1.2%. Predominant metabolites in urine 12 h after administration were M3 and M8, which accounted for 2.22 and 2.21% of the administered radioactivity respectively. Metabolites excreted in faeces 120 h after administration were very complex and poorly separated by hplc and could not be characterized: unchanged drug was not detected in the faeces.

Role of CYP3A in ethanol-mediated increases in acetaminophen hepatotoxicity

CYP2E is considered the only form of cytochrome P450 responsible for ethanol-mediated increases in acetaminophen hepatotoxicity. However, in experimental systems used for investigating ethanol-mediated increases in acetaminophen hepatotoxicity, animals are withdrawn from ethanol for 16 to 24 hr before the administration of acetaminophen to ensure the clearance of ethanol from the circulation. In rats, CYP2E has been shown to decrease to control levels after this time period of withdrawal from ethanol. We have previously shown in cultured human and rat hepatocytes, and in intact rats, that ethanol induces CYP3A in addition to CYP2E. To determine if there might be a role for CYP3A in ethanol-mediated APAP hepatotoxicity in addition to the recognized role for CYP2E, we investigated the effect of triacetyloleandomycin (TAO) on acetaminophen hepatotoxicity in ethanol-pretreated rats, as well as the effect of 11 hr withdrawal from ethanol on hepatic levels of CYP3A and CYP2E. TAO was dissolved in saline instead of dimethylsulfoxide, the solvent most usually employed, since dimethylsulfoxide inhibits CYP2E. Rats were administered 6.3% ethanol as part of the Lieber-DeCarli diet for 7 days, followed by replacement of the liquid diet with water for 11 hr. This 11-hr withdrawal from ethanol resulted in a decrease in hepatic levels of ethanol-induced CYP2E; however, considerable induction was still evident. There was no significant decrease in CYP3A. TAO completely prevented the histologically observed liver damage from acetaminophen in ethanol-pretreated rats, but did not prevent the increase in serum levels of AST. In ethanol-pretreated rats, exposure to APAP in the absence of TAO was associated with a 75% decrease in CYP3A, compared to animals exposed to APAP in the presence of TAO. These results suggest that CYP3A may have been suicidally inactivated by acetaminophen in the absence of TAO. Our findings suggest that CYP3A has a major role in ethanol-mediated increases in acetaminophen hepatotoxicity.

Effect of Taxol on cytochrome P450 3A and acetaminophen toxicity in cultured rat hepatocytes: comparison to dexamethasone

The purpose of this study was to determine if Taxol induced CYP3A in primary cultures of rat hepatocytes and, if so, whether induction of CYP3A would increase acetaminophen toxicity. Taxol caused a concentration-dependent increase in the amount of immunoreactive CYP3A and in the steady-state levels of CYP3A1/DEX but not CYP3A2 mRNA. Similar concentration-dependent increases in toxicity as measured by a decrease in protein synthesis were observed after exposure of cells to acetaminophen for 7 hr whether cells were pretreated with Taxol or dexamethasone. Increased release of lactate dehydrogenase occured after 24 hr exposure to acetaminophen, with no further decreases in protein synthesis than those observed at 7 hr. Increases in acetaminophen toxicity correlated with increased covalent binding of acetaminophen to cellular proteins. Triacetyloleandomycin, a selective inhibitor of CYP3A, completely protected the cells against acetaminophen toxicity in both Taxol- and dexamethasone-pretreated cells and prevented the increase in covalent binding of acetaminophen to cellular proteins. These results demonstrate that Taxol, like dexamethasone, induces CYP3A and that increases in this P450 are responsible for increased acetaminophen toxicity.

Acute hepatotoxicity of acetaminophen in rats treated with ethanol plus isopentanol

Acetaminophen (APAP) hepatotoxicity was investigated in rats fed ethanol and isopentanol alone or in combination in a liquid diet for 7 days. Serum levels of aspartate aminotransferase (AST) and histological examination of liver slices were used to assess hepatotoxicity. At 7 hr after intragastric administration of 0.5 or 1.0 g APAP/kg, there was no significant increase in serum levels of AST in rats treated with APAP alone, or in rats pretreated with ethanol or isopentanol alone followed by APAP. There was mild central lobular congestion in the livers of rats pretreated with ethanol alone followed by APAP. In contrast, in rats pretreated with the combination of ethanol and isopentanol, administration of APAP caused a dramatic increase in serum levels of AST, along with marked central lobular necrosis, including steatosis and ischemic changes. Hepatic glutathione levels were decreased to 40-50% of control values in APAP-treated rats that had been pretreated with ethanol either alone or in combination with isopentanol. The serum concentrations of APAP were significantly lower in rats pretreated with the combination of ethanol and isopentanol followed by 1 g APAP/kg than in rats treated with APAP alone, suggesting a greater rate of APAP metabolism. We had reported previously that combined treatment of rats with ethanol and isopentanol resulted in additive to synergistic increases in CYP3A, with no further increases in CYP2E than that caused by ethanol alone. CYP3A may, therefore, be responsible for the increased APAP hepatotoxicity caused by the combined alcohol treatment.

Ethanol and isopentanol increase CYP3A and CYP2E in primary cultures of human hepatocytes

In primary cultures of human hepatocytes prepared from three separate livers, ethanol increased both CYP3A and CYP2E1, as detected immunochemically. Isopentanol, the major higher chain alcohol in alcoholic beverages, also induced CYP3A and CYP2E1. Maximal increases in these P450s occurred at the lowest concentrations of isopentanol examined, 0.1 mM. Ethanol and isopentanol were each more potent and more effective at inducing CYP3A in the human hepatocytes than was previously shown in cultured rat hepatocytes. Steady-state levels of CYP3A3/4 mRNA were increased by both ethanol and isopentanol. Ethanol and isopentanol induced immunoreactive CYP3A to a greater extent than did phenobarbital. In all three cultures, the increases in CYP3A after treatment with ethanol were less than those observed after treatment with rifampicin, a highly effective inducer of CYP3A in human hepatocytes. In one human hepatocyte culture, the lowest concentration of isopentanol tested increased CYP3A protein to an amount similar to that increased by rifampicin. In another human hepatocyte culture, however, the amount of immunoreactive CYP3A increased by isopentanol was less than that increased by rifampicin. In this latter culture, the steady-state levels of CYP3A3/4 mRNA increased by 0.1 mM isopentanol and 1 microM rifampicin were similar. This is the first finding of induction of CYP3A in human hepatocytes by ethanol or isopentanol. The clinical significance of the findings is discussed.

Synergistic increases in rat hepatic cytochrome P450s by ethanol and isopentanol

The purpose of this study was to determine if isopentanol alone or in combination with ethanol increased CYP2B1/2, CYP2E or CYP3A in the livers of rats. Increasing doses of isopentanol (0.5, 1, 2 or 3%) were administered in combination with 5.6% ethanol in the Lieber-DeCarli liquid diet for 7 days. Doses of 0.5 or 3% isopentanol were also administered alone. Isopentanol alone caused small increases in CYP2B1/2 and CYP3A. However, when isopentanol (2 or 3%) was combined with ethanol a synergistic increase in P4502B1/2 was observed. The combined alcohol treatment also resulted in a greater increase in immunoreactive CYP3A than either alcohol alone. Ethanol alone increased CYP2E 5-fold. Inclusion of isopentanol with ethanol resulted in either small or no additional increases in CYP2E. These results confirm our previous findings in cultured hepatocytes that when isopentanol is combined with ethanol, there is a synergistic increase in CYP2B1/2. Increases in CYP2B1/2, CYP2E and CYP3A protein moieties by ethanol, and by ethanol in combination with isopentanol, were associated with increases in their mRNAs. Blood isopentanol levels were 10-fold greater in rats administered 3% isopentanol in combination with ethanol compared to rats administered 3% isopentanol alone. From these results we suggest that isopentanol, a higher chain alcohol in alcoholic beverages, can contribute to increases in hepatic cytochrome P450 observed following consumption of alcoholic beverages.

Disposition of the novel anticancer agent vinorelbine ditartrate following intravenous administration in mice, rats and dogs

1. KW-2307 (vinorelbine ditartrate, CAS71486-22-1) is a new semisynthetic antitumour vinca alkaloid. Its pharmacokinetics, distribution and excretion were investigated following intravenous administration to mice (1.2 mg/kg), rats (0.12 and 1.2 mg/kg) and dogs (0.4 mg/kg). Dose levels are expressed as the free base. 2. Plasma concentrations of drug-related radioactivity declined in a bi- or tri-exponential manner, initially rapidly and then slowly (half-life of 35 h or more). Unchanged drug concentrations declined with terminal half-lives of 35.8 h in rats and 34.5h in dogs: a terminal phase was not observed in mice. KW-2307 can be characterised as a drug of high clearance (3.78, 1.73 and 1.20 l/h/kg in the mice, rats and dogs, respectively) and large volume of distribution (12.7, 41.9 and 49.6 l/kg in the mouse, rat and dog, respectively). After repeated administrations for 21 days in the rat, the accumulation ratio for unchanged drug concentrations in plasma was 1.5. 3. The extent of binding of 3H-KW-2307 in vitro to proteins in the plasma of humans, dogs, rats and mice was 89, 90, 93 and 97%, respectively. 4. In rats, concentrations of radioactivity in most tissues exceeded those in plasma, and at 0.5 h after administration were greatest in the adrenals, thyroid, pituitary, lungs, small intestine contents and kidneys. The lung is a target for drug action. Concentrations of radioactivity in the brain were lowest. In pregnant rats, placental transfer of radioactivity was low, less than 1% of the dose. Concentrations in mammary tissue, another target for drug action, exceeded those in plasma. The tissue distribution profile of radioactivity in rats was similar after single and repeated administrations. 5. Radioactivity was excreted mainly in faeces (61-73% dose in 48 h and 71-79% dose in 168 h). Biliary excretion accounted for 42.6% dose in rats during 48 h although enterohepatic cycling was probably unimportant.

Critical care experience for baccalaureate nursing students

The projected need for critical care nurses can be met through the collaborative efforts of nursing education and nursing service. An approach as implemented at our institution with the support of community agencies can be mutually beneficial. It is generally recognized that new graduates tend to seek employment where they had positive student experiences. Although few students may choose critical care as a career, the majority will have a positive memory, which is supportive of the unique contribution of critical care nursing within the scope of the health and care of patients and their families.

Critical care experience for baccalaureate nursing students

The projected need for critical care nurses can be met through the collaborative efforts of nursing education and nursing service. An approach as implemented at our institution with the support of community agencies can be mutually beneficial. It is generally recognized that new graduates tend to seek employment where they had positive student experiences. Although few students may choose critical care as a career, the majority will have a positive memory, which is supportive of the unique contribution of critical care nursing within the scope of the health and care of patients and their families.

Synergistic induction of cytochrome P450 by ethanol and isopentanol in cultures of chick embryo and rat hepatocytes

The purpose of this study was to investigate whether isopentanol, the most abundant higher chain alcohol in alcoholic beverages, contributes to induction of different forms of hepatic P450s associated with consumption of these beverages. We have previously reported that ethanol and isopentanol each induce P450 2H1/2 in cultured chick hepatocytes and that ethanol induced P450 2B1/2, as well as P450 2E, in cultured rat hepatocytes. Here we investigated the induction of P450 by isopentanol alone and in combination with ethanol in cultured chick and rat hepatocytes. The forms of induced P450 were identified both enzymatically and immunochemically. In cultured chick hepatocytes, both isopentanol and ethanol induced P450 2E, but combined treatment with these alcohols had no greater effect than treatment with ethanol alone. In cultured rat hepatocytes, isopentanol alone did not induce P450 2E or 2B1/2 and had no effect on the ethanol-mediated induction of P450 2E. However, isopentanol combined with ethanol caused a synergistic induction of P450 2B1/2 in cultured rat hepatocytes and an additive to synergistic induction of P450 2H1/2 in cultured chick hepatocytes. The levels of enzyme activities induced by the combined alcohol treatment approached those induced by potent barbiturates. The results suggest that the pentanols in alcoholic beverages may be responsible for a barbiturate-like induction of P450 in hepatocytes.

Metabolism of the anti-psoriatic agent 5-methoxypsoralen in humans: comparison with rat and dog

1. Single oral doses of 14C-5-methoxypsoralen (5-MOP) to human subjects (50 mg), rats (1 mg/kg) and dogs (1 mg/kg) were fairly well absorbed but subjected to extensive first-pass metabolism, at least in rat and human. Means of 62, 51 and 40% dose in urine and 31, 38 and 48% dose in faeces, were excreted by humans (during 5 days), rats (3 days) and dogs (1 day), respectively. In dogs, faecal 14C was probably derived, in part, from biliary excreted material. 2. Total 14C in human plasma reached peak concentrations after 2 h (mean 235 ng 5-MOP equivalent/ml) and declined relatively slowly, to about 60% of this value within 24 h. Unchanged 5-MOP was not detected in plasma using h.p.l.c. (< 5 ng/ml). 3. Tissue concentrations of 14C were generally greater in dogs than rats and reached peak levels at 1 h in dogs but at 24 h in rats. Apart from liver and bile, dog tissue 14C concentrations were lower than those in the corresponding plasma, whereas in rat they were lower only until the time of peak concentrations, after which they were generally greater. 4. 5-MOP was extensively metabolized in all three species. The major 14C-components in human and dog urine were glucuronic acid conjugates, mainly of an arylacetic acid and arylalcohols, resulting from initial oxidative metabolism of the furan ring of 5-MOP. In rat, these metabolites were excreted mainly unconjugated. An unusual metabolite was formed by reduction of the lactone moiety of 5-MOP, probably by the gut flora, giving rise to an arylpropionic acid, excreted as a glucuronic acid conjugate in the urine of all three species. 5. Unchanged drug was a very minor component of human and rat plasma, but a major component of dog plasma. In all three species, circulating 14C-metabolites were similar to those in the urine but were present mainly unconjugated. On the basis of these data, the metabolic fate of 5-MOP in humans was more similar to that in dog than to that in rat, although humans appeared to metabolize 5-MOP more rapidly than did dog.

2-Amino-3,4-dimethylimidazo[4,5-f]quinoline induces and inhibits cytochrome P450 from the IA subfamily in chick and rat hepatocytes

Several heterocyclic amines, found in cooked food, are powerful mutagens in the Ames Salmonella mutagenicity test system. One of these, 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ) is one of the most mutagenic chemicals tested in this assay. In primary cultures of chick and rat hepatocytes, MeIQ, by itself, induced cytochrome P450 from the IA subfamily but was a weak inducer compared to 3-methylcholanthrene. However, in both chick and rat hepatocytes in culture, MeIQ decreased the amount of 3-methylcholanthrene-induced ethoxyresorufin deethylase activity, which is catalyzed by cytochrome P450 IA. The protein moiety of cytochrome P450 IA was decreased at MeIQ concentrations of 2.5 micrograms/ml or greater in chick hepatocytes and 25 micrograms/ml in rat hepatocytes. In hepatic microsomes from methylcholanthrene-treated chicks and rats, MeIQ was a competitive inhibitor of both ethoxyresorufin deethylase activity, a reaction catalyzed mainly by rodent cytochrome P450 IA1, and uroporphyrinogen oxidation, a reaction catalyzed by rodent P450 IA2. In cultured chick hepatocytes, MeIQ also decreased cytochrome P450-mediated oxidation of uroporphyrinogen by intact cells. The ability of MeIQ to inhibit as well as to induce cytochrome P450s of the IA subfamily may be important in assessing the mutagenic and carcinogenic effects of MeIQ in mammals.

Evaluation of the antiviral activity of anthraquinones, anthrones and anthraquinone derivatives against human cytomegalovirus

A number of anthraquinones, anthrones and anthraquinone derivatives were evaluated for antiviral activity against human cytomegalovirus (HCMV) as well as for cytotoxicity. Of those compounds evaluated, quinalizarin, emodin, rhein, hypericin, protohypericin, alizarin, emodin bianthrone and emodin anthrone showed antiviral activity against a normal laboratory HCMV strain, AD-169. When tested against a ganciclovir-resistant strain of HCMV, the EC50 values for quinalizarin, rhein and alizarin were superior to the values obtained for the AD-169 strain of HCMV. These results suggest that these compounds will be useful as prototypes for synthesizing a class of anti-HCMV drugs that are effective against ganciclovir-sensitive and -resistant strains of HCMV.

Studies of the pharmacokinetics and metabolism of 4-amino-propiophenone (PAPP) in rats, dogs and cynomolgus monkeys

The pharmacokinetics and metabolism of 4-aminopropiophenone (PAPP), a cyanide antidote, have been studied in rats, dogs and cynomolgus monkeys using 14C-PAPP. Radiolabelled material was rapidly excreted in all three species, mainly in urine. In rats, PAPP was metabolized by N-acetylation, while in dogs, ring and aliphatic hydroxylation occurred. In monkeys, both N-acetylation and oxidation took place. In the latter pathway, PAPP was oxidized to p-aminobenzoic acid which underwent amino acid-conjugation to p-aminohippuric acid. In rat blood in vitro, the PAPP metabolites, p-aminobenzoic, p-aminohippuric and N-acetyl-p-aminobenzoic acid were only weak methaemoglobin producers.

In vitro virucidal activity of selected anthraquinones and anthraquinone derivatives

Anthraquinones and anthraquinone derivatives were characterized for their antiviral and virucidal activities against viruses representing several taxonomic groups. One of these compounds, hypericin, had activity against vesicular stomatitis virus, herpes simplex virus types 1 and 2, parainfluenza virus, and vaccinia virus (from 0.5 to 3.8 log10 reductions in infectivity) at concentrations of less than 1 microgram/ml as determined by a direct pre-infection incubation assay. Human rhinovirus was not sensitive to hypericin at concentrations up to 10 micrograms/ml. Addition of small amounts of Tween-80 to solutions containing hypericin enhanced, by up to 2.6 log10, hypericin's virucidal activity. Anthraquinones and anthraquinone derivatives with the hydroxyl and alkyl substitution pattern of emodin (i.e. emodin, emodin anthrone, emodin bianthrone and hypericin) were active against the enveloped viruses tested. The following general pattern of activity was found: hypericin greater than emodin bianthrone greater than emodin anthrone greater than emodin. Chrysophanic acid, aloe-emodin, and sennosides A and B did not possess activity against any of the viruses tested.

Nucleic acid related compounds. 65. New syntheses of 1-(beta-D-arabinofuranosyl)-5(E)-(2-iodovinyl)uracil (IVAraU) from vinylsilane precursors. Radioiodine uptake as a marker for thymidine kinase positive herpes viral infections

(Trimethylsilyl)acetylene was coupled with 1-(2,3,5-tri-O-acetyl-beta-D- arabinofuranosyl)-5-iodouracil to give 1- (2,3,5-tri-O-acetyl-beta-D-arabinofuranosyl)-5-[2-(trimethylsilyl)eth yny l] uracil. Lindlar hydrogenation of 4 gave 1-(2,3,4-tri-O-acetyl-beta-D-arabinofuranosyl)-5(Z)-[2- (trimethylsilyl)vinyl]uracil. Treatment of 5 with iodine monochloride (or sodium iodide/phenyliodine(III) dichloride) in benzene gave 1-(2,3,5-tri-O-acetyl-beta-D-arabinofuranosyl)-5(E)-(2-iodovinyl)uracil (7), whereas polar solvents favored the (Z)-iodovinyl isomer 8. Deacetylation of 7 gave 1-(beta-D-arabinofuranosyl)-5(E)-(2-iodovinyl)uracil (IVAraU, 9). A microscale in situ synthesis with Na*I gave [*I]IVAraU. Treatment of HSV-infected cells with [125I]IVAraU resulted in virus-dependent uptake associated with nucleoside phosphorylation by wild type or acyclovir-resistant DNA polymerase mutants (but not with TK-HSV-1 mutants). Uptake was virus-inoculum dependent and was detectable within 4 h postinfection. The process was not completely reversible. Virus-specified uptake of [125I]IVAraU may allow automated in vitro detection of HSV isolates.

Critical care concepts in baccalaureate nursing education

The high response rate of 65.1 percent to this survey suggests nurse educators across the country are interested and involved with the incorporation of critical care concepts in baccalaureate nursing education. Nurse educators are conscientiously working to provide an educational basis for graduate nurses to adequately address the complex healthcare needs of our society. Cooperative efforts between nurse educators and practicing critical care nurses can make a difference in the future delivery of healthcare.

HPLC analysis of allicin and other thiosulfinates in garlic clove homogenates

Reversed-phase high Performance liquid chromatography (C18-HPLC) was used to separate and quantitate all the detectable alkyl and alkenyl thiosulfinates, including configurational isomers, of garlic homogenates. Pure thiosulfinates were synthesized or isolated and identified by (1)H-NMR, and their extinction coefficients determined. Some configurational isomers required Separation by silica-HPLC. Five previously unreported thiosulfinates have been found, four of which contain the TRANS-1-propenyl group and increase several-fold to over half the content of allicin upon storage of garlic bulbs at 4 degrees C with a concomitant decrease in a gamma-glutamyl peptide. The variation in thiosulfinate yield between different countries, stores, bulbs, cloves, and storage times was investigated. A method for standardizing the quantitation of allicin yield from garlic is proposed and compared to other methods of allicin analysis.

Critical care concepts in baccalaureate nursing education

The high response rate of 65.1 percent to this survey suggests nurse educators across the country are interested and involved with the incorporation of critical care concepts in baccalaureate nursing education. Nurse educators are conscientiously working to provide an educational basis for graduate nurses to adequately address the complex healthcare needs of our society. Cooperative efforts between nurse educators and practicing critical care nurses can make a difference in the future delivery of healthcare.

The formation of methaemoglobin by 4-aminopropiophenone (PAPP) and 4-(N-hydroxy) aminopropiophenone

Oral dosing of rats with the cyanide antidote 4-aminopropiophenone (PAPP), brought about peak methaemoglobin levels at 15-40 min, but peak levels were attained at at 15-25 min after intravenous dosing. After both oral and intravenous administration at equimolar doses, 4-(N-hydroxy)aminopropiophenone (PHAPP), the putative methaemoglobin-producing metabolite of PAPP, produced higher peak levels of methaemoglobin than PAPP. Plasma from rats injected with PAPP was capable of forming methaemoglobin when added to naive rat erythrocytes. The identity of the metabolite responsible is discussed.

Synthetic peptide substrates for the immunoglobulin A1 protease from Neisseria gonorrhoeae (type 2)

Neisseria gonorrhoeae secretes protease which inactive human immunoglobulin A1 (IgA1) by cleavage of specific peptide bonds in the hinge region. The type 2 IgA1 protease (EC 3.4.24.13) is secreted as a 169-kDa precursor which undergoes autoproteolysis at three sites (A, B, and C) to release the 106-kDa active form of the enzyme (J. Pohlner, R. Halter, K. Beyreuther, and T. F. Meyer. Nature [London] 325:458-462, 1987). Synthetic decapeptides consisting of five residues on each side of the three autoproteolytic cleavage sites and their potential pentapeptide catabolites were prepared by solid-phase synthesis. Cleavage of the decapeptides by the type 2 IgA1 protease from N. gonorrhoeae was monitored by high-performance liquid chromatography. Peptides homologous with the amino acid sequences around the B and C sites are cleaved by the IgA1 protease. Amino acid analysis and Edman degradation show that the cleavage products have both the composition and amino acid sequence which would be expected from cleavage at the predicted sites. Km values of 1.35 mM and 3.43 mM and kcat values of 280 pmol/h/U and 439 pmol/h/U for the site B and site C peptides, respectively, were determined. The catalytic efficiency (kcat/Km) for the synthetic substrates is about 10% of that reported for intact IgA1. Cleavage of the peptides is inhibited by IgA1 protease inhibitors such as the tetrapeptide substrate analog inhibitor HRP-48, human colostrum, and a peptide-boronate transition state inhibitor. An extract from an N. gonorrhoeae construct lacking active IgA1 protease failed to cleave the synthetic substrate, while an extract from the control construct which secretes active enzyme completely hydrolyzed the synthetic peptide. Neither the site A peptide nor synthetic decapeptides encompassing cleavage sites in the hinge region of IgA1 are hydrolyzed by IgA1 protease. These are the first synthetic substrates to be reported for any IgA1 protease.

Hemolysis of erythrocytes and fluorescence polarization changes elicited by peptide toxins, aliphatic alcohols, related glycols and benzylidene derivatives

Hemolysis rates of human erythrocytes induced by C2 and C8-C14 straight chain 1-alkanols, 1,2-alkanediols and the corresponding benzylidene derivatives (benzaldehyde acetals) have been studied and compared with hemolysis rates obtained by three peptide toxins. The peak of activity occurs at C12 for the alkanols and glycols and at C10 for the benzylidene derivatives. The most active compound is 1-dodecanol, followed by 1,2-dodecanediol and the C10 benzylidene acetal, which show 50% hemolysis at 15, 99 and 151 microM, respectively, at 37 degrees C. A few lysolecithins and longer chain cis-unsaturated alcohols were studied for comparison purposes, and were found to be more active than 1-dodecanol. The most active were the 16:0 lysolecithin and cis-9-tetradecene-1-ol, which gave 50% hemolysis at concentrations of 2.8 and 5.6 microM respectively. The hemolytic activities of 1-dodecanol, 1,2-dodecanediol and the C10 benzylidene acetal were compared to activities of Pyrularia thionin and melittin with cow, horse, sheep, pig and human erythrocytes. Whereas the peptide toxins showed clear specificity for human erythrocytes, no selectivity was shown by any of the other compounds tested. Addition of the thionin or Naja naja kaouthia cardiotoxin to erythrocyte ghosts caused a slight but reproducible increase in the order of the phospholipid bilayer, as measured with the fluorescent probe NBD-PC. Cardiotoxin gave a greater response than did the P thionin, and extensively iodinated P thionin gave a smaller change than did P thionin. Similar results were obtained with melittin, but this peptide gave a markedly greater response than all other peptides. Addition of dodecanol or the C10 benzylidene acetal caused a marked increase in membrane fluidity. All of these data indicate that the organic compounds interact directly with and are incorporated nonspecifically into the membrane lipid bilayer, but the peptide toxins interact specifically with some component on the surface of the membrane, either a protein or specific phospholipid domain, followed by insertion into the membrane and decreasing phospholipid movement.

Tetrapeptide inhibitors of the IgA1 proteinases from type I Neisseria gonorrhoeae

The six series of unique tetrapeptides and their blocked N-acetyl, C-amide, and N-acetyl-C-amide analogues which comprise the hinge region of human IgA1 (Ser224 to Ser240) have been synthesized and tested as inhibitors of the type 1 IgA1 proteinase elaborated by Neisseria gonorrhoeae (EC 3.4.24.13). Most series had at least one member with an IC50 value less than 1 mM. The most effective inhibitors came from the series Ser-Thr-Pro-Pro (P4-P1) and Pro-Thr-Pro-Ser (P1-P3'). One member from each series had an IC50 value in the low microM range. Magnetic resonance studies (Siemion, I. Z.; et al. Biophys. Chem. 1988, 31, 35) indicate that the various tetrapeptide series appear to have different preferred solution conformations. However, these do not appear to be correlated with affinity for the neisserial proteinase. The most effective inhibitors tend to have a threonine residue adjacent to the N-terminus and the P1 or P1' residues at either the N- or the C-terminus. These relationships are not exclusive however, as other inhibitors, which do not meet these criteria, bind reasonably well. The most effective substrate analogues outlined here are about one-half the size and bind to the neisserial proteinase 2 orders of magnitude more tightly than previously reported inhibitors.