Modulation of in vivo 3-deoxyglucosone levels.

Fructoselysine 3-phosphate is synthesized in vivo by the recently discovered fructoseamine-3-kinase (F3K) from fructoselysine and ATP and decomposes to lysine, P(i) and 3-deoxyglucosone (3DG). This pathway appears to dominate 3DG production in vivo, making it possible to modulate 3DG levels by stimulating or inhibiting the reaction. Present inhibitors are non-reacting substrate analogues with relatively high K (i) values and can inhibit F3K sufficiently in vivo to reduce 3DG in diabetic rat plasma by approx. 50%. Stimulation of the F3K pathway by feeding glycated casein causes an increase of 10-20-fold in plasma levels of 3DG and 3-fold in kidney tubules. Consequences of this increase were studied in two systems: the Eker rat, a model of susceptible kidney tubules; and birth rates in two rat strains. In both cases substantial pathological effects were observed. In the Eker rats, an approx. 3-fold increase in kidney lesions was observed ( P <0.00001). In both Fischer 344 and Sprague-Dawley rats, birth rates were reduced by 56% ( P <0.0001) and 12% ( P <0.015) respectively. These results suggest that inhibition of F3K is a promising new therapeutic target for diabetic complications, as well as other 3DG-dependent pathologies.

Pharmacokinetics, safety, and antiviral effects of hypericin, a derivative of St. John's wort plant, in patients with chronic hepatitis C virus infection.

Hypericin is a natural derivative of the common St. Johns wort plant, Hypericum perforatum. It has in vitro activity against several viruses, including bovine diarrhea virus, a pestivirus with structural similarities to hepatitis C virus (HCV). We conducted a phase I dose escalation study to determine the safety and antiviral activity of hypericin in patients with chronic HCV infection. The first 12 patients received an 8-week course of 0.05 mg of hypericin per kg of body weight orally once a day; 7 patients received an 8-week course of 0.10 mg/kg orally once a day. At the end of the 8-week period of treatment, no subject had a change of plasma HCV RNA level of more than 1.0 log(10). Five of 12 subjects receiving the 0.05-mg/kg/day dosing schedule and 6 of 7 subjects receiving the 0.10-mg/kg/day dosing schedule developed phototoxic reactions. No other serious adverse events associated with hypericin use occurred. The pharmacokinetic data revealed a long elimination half-life (mean values of 36.1 and 33.8 h, respectively, for the doses of 0.05 and 0.1 mg/kg) and mean area under the curve determinations of 1.5 and 3.1 microg/ml x hr, respectively. In sum, hypericin given orally in doses of 0.05 and 0.10 mg/kg/d caused considerable phototoxicity and had no detectable anti-HCV activity in patients with chronic HCV infection.

DYN 12, a small molecule inhibitor of the enzyme amadorase, lowers plasma 3-deoxyglucosone levels in diabetic rats.

3-Deoxyglucosone (3DG) is a highly reactive alpha-dicarbonyl sugar and potent protein cross-linker that is important in the formation of advanced glycation end products (AGEs), which have been postulated to lead to the development of diabetic complications. (1) Reducing 3DG levels in diabetics is a potentially effective therapy to slow the development of diabetic complications. Standard biochemical methods were used to isolate, identify, and characterize the enzyme responsible for the production of 3DG, in order to develop an effective therapeutic agent against this target. We have purified and characterized Amadorase, a fructosamine-3-kinase, and demonstrated both in vitro and in vivo that it is responsible for the production of 3-deoxyglucosone (3DG). A small molecule inhibitor of Amadorase, DYN 12, significantly lowered plasma levels of 3DG in diabetic (by 46%, p = 0.0116) and normal (by 43%, p = 0.0024) rats. These data are the first indications that it is possible to significantly reduce 3DG production in diabetics and thus possibly reduce the development of diabetic complications.

Subchronic and chronic toxicological investigations on metiram: the lack of a carcinogenic response in rodents.

Metiram complex is a non-systemically acting fungicide of the group of ethylenebisdithiocarbamates (EBDC). The subchronic and chronic toxicity and the carcinogenic potential of metiram (containing 2% ethylene thiourea, ETU, as an intentionally added impurity) were investigated. Doses in the chronic/carcinogenicity rat study were 0, 5, 20, 80, or 320 ppm. In the carcinogenicity study in mice, diets were administered for 89 weeks (females) or 95 weeks (males) at doses of 0, 100, 300, or 1000 ppm. No oncogenic response was noted in either species. The subchronic studies in rats and mice further investigated the thyroid as a target organ. Doses of 0, 5, 80, 320, or 960 ppm were utilized in the rat study and a NOAEL of 80 ppm was established. In the subchronic mouse study, diets containing 0, 300, 1000, 3000, or 7500 ppm were utilized. A NOAEL of 300 ppm was established in this study. In summary, the findings of these studies defined the toxicity of metiram in rodents and demonstrated the lack of a carcinogenic response following chronic dietary exposure in the rat and mouse. The NOAELs that were established in these studies were consistent with the NOAELs established for thyroid toxicity/carcinogenicity in studies on ethylenethiourea (ETU).

Photoactivated hypericin is an anti-proliferative agent that induces a high rate of apoptotic death of normal, transformed, and malignant T lymphocytes: implications for the treatment of cutaneous lymphoproliferative and inflammatory disorders.

Hypericin is a photodynamic compound activated by either visible (400-700 nm) or UVA (320-400 nm) light, and has been shown to inhibit the growth of a variety of neoplastic cell types. In this study, hypericin was found to inhibit proliferative responses of malignant T cells derived from the blood of patients with cutaneous T cell lymphoma. Control cells included peripheral blood mononuclear cells (PBMC) from normal volunteers or Epstein-Barr virus-transformed lymphocytes. Cells from each of these populations were incubated with serial dilutions of hypericin or 8-methoxypsoralen and then stimulated with the mitogen ConA (10 microg per ml). Cultures were prepared in the dark to minimize photoactivation of the hypericin. Proliferation was measured by [3H]thymidine labeling after 72 h. Hypericin, photoactivated with 1.1-3.3 J white light per cm2, inhibited cellular proliferation of malignant T cells with IC50 values from 0.34 to 0.53 microM, normal PBMC with IC50 values of 0.11-0.76 microM, and Epstein-Barr virus-transformed cells with IC50 values of 0.75-3.2 microM. UVA-photoactivated hypericin (0.5-2.0 J per cm2) could also inhibit proliferation with IC50 values of 0.57-1.8 microM, 0.7-4.6 microM, and 2.0-3.7 microM for malignant, normal, or Epstein-Barr virus-transformed cells, respectively. Hypericin, photoactivated with either UVA or white light, could induce near complete apoptosis (94%) in malignant cutaneous T cell lymphoma T cells, whereas lower levels of apoptosis (37-88%) were induced in normal PBMC. These data indicate that hypericin inhibits mitogen-induced proliferation of malignant T cells from patients with cutaneous T cell lymphoma, PBMC from normal individuals, as well as Epstein-Barr virus-transformed lymphocytes, and that inhibition of cell proliferation is dependent on the concentration of hypericin used and the dose of light required to photoactivate the compound. Induction of apoptosis is, in part, one mechanism by which photoactivated hypericin inhibits malignant T cell proliferation.

A critique of the World Resources Institute's report "Pesticides and the immune system: the public health risks".

A recent World Resources Institute (WRI) report concluded that pesticides are a likely cause of immune suppression for millions of people throughout the world. The gravity of this conclusion motivated us to review the scientific evidence cited in the report. The predominant human evidence came from cross-sectional studies conducted in the former Soviet Union. These studies were difficult to evaluate due to incomplete reporting and had obvious limitations in terms of subject selection, exposure assessment,lack of quality control, statistical analysis, adequacy of the comparison group, and confounding. The toxicologic evidence was comprised mainly of acute high-dose studies in which the exposure conditions resulted in systemic toxicity. The relevance of these studies to effects at typical human exposure levels is questionable. We did not find consistent, credible evidence to support the conclusion of widespread pesticide-related immune suppression. Nonetheless, the WRI report is an important document because it focuses attention on a potentially important issue for future research and brings a substantial literature of foreign language studies to the attention of Western scientists.

FIFRA Subdivision F testing Guidelines: are these tests adequate to detect potential hormonal activity for crop protection chemicals? Federal Insecticide, Fungicide, and Rodenticide Act.

Recently, a major topic of discussion has been the impact of synthetic chemicals that possess the capacity to alter hormonal activity, the so-called "endocrine modulators," with potentially the capacity to alter the reproductive capability of humans. Particularly, various synthetic pesticides and industrial chemicals that persist in the environment and/or bioaccumulate have been implicated. Further, it has been alleged that the standard tests for pesticide registration as required by the U.S. Environmental Protection Agency (EPA) and other regulatory agencies may be inadequate to detect endocrine modulating effects. To address these shortcomings, it has been proposed that very specific tests for estrogen receptor binding, or in vitro cell response to chemicals, be used to identify potential endocrine modulators. However, such approaches have certain flaws that limit their application as screens. First, very specific tests, like receptor binding, evaluate only a single chemical event per test. Such tests do not measure toxicity or biological response. Isolated systems are very important for studying mechanisms of action or structure activity relationships, but can only provide a preliminary screen for a single mechanism of toxicity. Isolated systems can not be used to regulate a chemical without additional information. Second, they fail to test many other parts of the neuroendocrine control of the reproductive system. Testing for adverse effects in highly specific in vitro systems failed to replace whole-animal models in carcinogenesis and will also fail in reproductive toxicology because this system is too complicated for such as in vitro approach to be accurately predictive. Advanced tests, such as the EPA multigeneration study, are more effective, and reliable means for evaluation than any specific and narrowly focused screening tests. Experience has shown that a better approach to testing chemicals is to evaluate their effects on the whole animal. When one part of the system is adversely affected, various processes may be indirectly affected and can be detected in the animal model. For example, a modulation of testosterone synthesis could lead to (1) altered accessory sex organ morphology, size, and function; (2) decreased sperm counts; and (3) even decreased fertility. These and many other effects would be noted in toxicity studies that are already required for the registration of crop protection chemicals. The developmental and reproductive toxicity guidelines were recently reviewed in a hearing that included the representatives from the EPA, the public, and the Scientific Advisory Panel. The EPA kept the basic study design the same, but added a few new endpoints to further assess chemical-induced effects on reproductive development and function. The review presented herein concentrates on the required Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) testing for pesticides, and demonstrates how the massive arrays of sensitive endocrine endpoints that are delineated in FIFRA Subdivision F have been successfully used to detect both weak and potent hormonally modulating chemicals. For example, (1) diethyl-stilbestrol (DES), which is a potent synthetic therapeutic estrogen, (2) DDT, which is weakly estrogenic but persistent and bioaccumulating, and (3) dioxins, which have antiestrogenic properties, were all found as being hormonally active in tests similar or identical to FIFRA tests. All food-use pesticides have been evaluated using a comprehensive multigeneration reproduction test. Hence, the FIFRA testing procedures have been demonstrated to identify endocrine modulators of sufficient potency to represent a concern to human health.

In vitro and in vivo antibacterial activities of levofloxacin (l-ofloxacin), an optically active ofloxacin.

The antibacterial activity of levofloxacin was compared with those of ofloxacin, ciprofloxacin, and other antibiotics. In general, levofloxacin was equally active or up to fourfold more active than ofloxacin against all 801 organisms tested. Levofloxacin was twofold [corrected] more active than ciprofloxacin against Streptococcus pneumoniae and 2- to 4-fold more active than ciprofloxacin against Staphylococcus aureus, Xanthomonas maltophilia, and Bacteroides fragilis. Levofloxacin was two- to eightfold more active than ciprofloxacin against coagulase-negative staphylococci and Acinetobacter spp., although these improvements in potency may not be clinically relevant. Levofloxacin inhibited 90% of streptococci when it was used at concentrations of 1 to 2 micrograms/ml. Levofloxacin was two- to fourfold less active than ciprofloxacin against most members of the family Enterobacteriaceae, such as Escherichia coli; Klebsiella pneumoniae; Citrobacter, Proteus, Providencia, Salmonella, and Yersinia spp.; and Pseudomonas aeruginosa. Both compounds were equally active against Pseudomonas cepacia. The in vitro DNA gyrase inhibitory activity of levofloxacin was as potent as that of ciprofloxacin, with a 50% inhibitory concentration of 0.65 micrograms/ml against an E. coli enzyme. In vivo, oral treatment with levofloxacin was as efficacious or more efficacious than that with ciprofloxacin in systemic as well as pyelonephritis infections in mice. Levofloxacin achieved higher concentrations in the serum and tissue of mice than did ciprofloxacin. This study presents some potential advantages of the pure L isomer of ofloxacin over ciprofloxacin and other quinolones.

Bemoradan--a novel inhibitor of the rolipram-insensitive cyclic AMP phosphodiesterase from canine heart tissue.

Canine cardiac muscle contains a type IV cyclic AMP (cAMP) phosphodiesterase (PDE) that is composed of two subtypes. One subtype is sensitive to rolipram inhibition (RSPDE), whereas the other is not inhibited significantly by rolipram (RIPDE). The RIPDE is inhibited by several cardiotonic agents operating by a PDE-inhibitory mechanism. Bemoradan [RWJ-22867; 7-(1,4,5,6-tetrahydro-4-methyl-6-oxo-3-pyridazinyl)-2H-1,4-benzoxazin -3(4H)-one], a novel, potent positive inotropic agent, demonstrated biphasic inhibition of the fraction III enzyme from canine cardiac muscle. Inhibition by rolipram of the RSPDE converted the IC50 curves of bemoradan, indolidan, pimobendan, and imazodan to sigmoidal, monophasic curves. Lineweaver-Burk analysis yielded competitive inhibition KI values of 0.023, 0.09, 0.065 and 0.60 microM, respectively, for these compounds. The cardiotonic compounds, however, were not potent inhibitors of the Type I and Type II cAMP PDEs found in canine ventricular muscle. The order of potency for inhibiting the RIPDE cAMP PDE subtype was bemoradan greater than pimobendan greater than indolidan greater than imazodan. Bemoradan is, therefore, a potent inhibitor of the cardiac muscle cAMP PDE which could, in part, be responsible for its cardiotonic activity.

In-vivo evaluation of ofloxacin in Salmonella typhimurium infection in mice.

The effects of ofloxacin in Salmonella typhimurium infection in mice were compared with those of ciprofloxacin, ampicillin and chloramphenicol. Oral administration of ofloxacin at 10, 50 or 100 mg/kg once per day for seven days significantly (P less than 0.02) increased survival (20.1 days at 100 mg/kg) of infected mice relative to non-treated controls (4.1 days). In addition, after oral treatment with 100 mg/kg of each of the antibiotics, ofloxacin was significantly more effective than ampicillin (9.9 days), chloramphenicol (8.4 days) or ciprofloxacin (14.9 days) in prolonging the mean survival time of these mice. A comparison of oral potencies indicates that ofloxacin is five times more potent than ciprofloxacin (oral ED50 = 13.3 mg/kg vs ciprofloxacin = 69.9 mg/kg) and over eight times more potent than either of the other two antibiotics. When the number of bacteria from livers and spleens was quantitated, only ofloxacin (25 or 100 mg/kg,po) significantly (P less than 0.02) reduced the number of viable bacteria in both of these tissues in comparison with untreated controls, and, relative to the other antibiotics, ofloxacin (100 mg/kg) caused a significantly greater reduction. Single oral dosing of 20 mg/kg of either ofloxacin or ciprofloxacin showed that ofloxacin achieves approximately a four-fold higher peak serum or liver concentration than ciprofloxacin, which may contribute to its better efficacy in this infection model. These results taken together suggest that oral ofloxacin may be of value in treating systemic salmonella infections in humans.

6-Benzoxazinylpyridazin-3-ones: potent, long-acting positive inotrope and peripheral vasodilator agents.

A series of 6-benzoxazinylpyridazin-3-ones was prepared and evaluated for inhibition of cardiac phosphodiesterase (PDE) fraction III in vitro and for positive inotropic activity in vivo. 6-[3,4-Dihydro-3-oxo-1,4(2H)-benzoxazin-7-yl]-2,3,4,5-tetrahydro-5 - methylpyridazin-3-one (bemoradan) was found to be an extremely potent and selective inhibitor of canine PDE fraction III and a long-acting, potent, orally active inotropic vasodilator agent in various canine models. Additional benzoxazin-6-yl and -8-yl compounds were also prepared. Altering the pyridazinone substitution from the 6-position to the 7-position produced a 14-fold increase in the iv cardiotonic potency (ED50) from 77 to 5.4 micrograms/kg while substitution at the 8-position reduced potency. Methyl substitution at various sites in the molecule was also examined. Positive inotropic activity was maintained for between 8 and 24 h after a single oral dose (100 micrograms/kg) of bemoradan in dogs, thus making it one of the most potent and long-acting orally effective inotropes yet described. Bemoradan is currently under development as a cardiotonic agent for use in the management of congestive heart failure.

Positive inotropic and hemodynamic properties of flosequinan, a new vasodilator, and a sulfone metabolite.

Flosequinan, a new orally active vasodilator, and its sulfone metabolite were evaluated for inotropic activity in isolated ferret papillary muscles and pentobarbital anesthetized open-chest dogs. In vitro, flosequinan and its sulfone derivative increased tension development in a concentration-dependent manner (1-50 microM) in electrically stimulated papillary muscles pretreated with the beta-adrenergic blocking agent atenolol (2 microM). Peak increases in tension of 75 +/- 17%, and 111 +/- 46% with potencies (EC50) of 15 and 10 microM were observed for flosequinan and its metabolite, respectively. In vivo, flosequinan increased left ventricular dP/dtmax (74 +/- 12%) and right ventricular contractile force (CF) (104 +/- 10%) after administration of 1.875 mg/kg, i.v. Inotropic activity was dose-dependent and remained elevated for at least 60 min postinfusion. Flosequinan also increased heart rate (HR) (14 +/- 2%) and reduced mean arterial pressure (-9 +/- 3%). The i.v. potency of flosequinan (ED50 = 0.45 mg/kg) and its metabolite (ED50 = 0.38 mg/kg) were similar to that of the inotropic vasodilator amrinone (ED50 = 0.38 mg/kg). Inotropic activity was not significantly altered by pretreatment with propranolol (0.5 mg/kg) and atropine (1.0 mg/kg), further supporting the in vitro data indicating that flosequinan can directly stimulate myocardial contractility independent of beta-adrenergic receptor activation. Additional hemodynamic studies were conducted in an acute heart failure model produced by an overdose of propranolol. Flosequinan (2 mg/kg, i.v.) increased cardiac output (CO) (50 +/- 9%) and stroke volume (SV) (29 +/- 8%) while reducing total peripheral vascular resistance (TPR) (-36 +/- 4%), right atrial pressure (-62 +/- 5%), and left ventricular end-diastolic pressure (LVEDP) (-41 +/- 2%).(ABSTRACT TRUNCATED AT 250 WORDS)

Renal vasodilators. The role of the 4-substituent in isoquinolin-3-ol cardiovascular agents: 4-ureido derivatives of isoquinolin-3-ol with selective renal vasodilator properties.

The synthesis and cardiovascular evaluation of a series of isoquinolin-3-ol derivatives bearing a variety of nitrogen substituents (amino, acylamino, carbamate, and ureido) at C-4 are described. Certain of these compounds have a selective renal vasodilating profile and have minimal effects on arterial blood pressure or heart rate when administered intravenously in the instrumented anesthetized dog. The most potent renal vasodilator in the series is 4-(allylureido)-6,7-dimethoxyisoquinolin-3-ol (38), which at a dose of 1.2 mg/kg iv produces a 97% maximal increase in renal blood flow without significant hypotensive or chronotropic effects. Structure-activity observations on the nature of the 4-substituent and the alkoxy substitution pattern in the aromatic ring of the isoquinolinol nucleus are discussed.

Increased vasodilator responsiveness to BRL 34915 in spontaneously hypertensive versus normotensive rats: contrast with nifedipine.

The blood pressure-lowering potency and activity of BRL 34915, a new vasodilator and putative stimulator of potassium efflux from vascular smooth muscle, was investigated in conscious spontaneously hypertensive rats (SHR) and normotensive rats (NTR) after intravenous administration and compared with that of the calcium channel blocker, nifedipine. In SHR, BRL 34915 (3-100 micrograms/kg) or nifedipine (10-3000 micrograms/kg) produced similar reductions in mean arterial pressure of 58 +/- 3% and 55 +/- 3%, respectively. BRL 34915 (ED30% = 13.8 micrograms/kg) was 15.3 times more potent than nifedipine (ED30% = 207 micrograms/kg) in SHR. In contrast, only a 1.7-fold difference in potency was observed in NTR between BRL 34915 (ED30% = 123 micrograms/kg) and nifedipine (ED30% = 182 micrograms/kg). The potency ratio (ED30% NTR/ED30% SHR) for BRL 34915 was 8.83 whereas nifedipine had a ratio of 0.88, reflecting the greater responsiveness of the SHR to BRL 34915. Systemic hemodynamics were monitored in anesthetized SHR and NTR to determine the basis for the reductions in blood pressure. BRL 34915 (3-100 micrograms/kg iv) lowered mean arterial pressure in both groups solely by decreasing total peripheral vascular resistance, since no changes in cardiac output were observed. Relaxation responses were also obtained in phenylephrine-contracted isolated aortic strips from both strains of rat to ascertain whether differences in responsiveness existed at this level of the vasculature. No significant difference in the potency of BRL 34915 (3-10 microM) as a vasodilator was found in aortas from SHR or NTR. These results indicate that, unlike nifedipine, BRL 34915 is a more potent vasodepressor agent in SHR than in NTR and suggests that the potassium efflux stimulator may preferentially relax resistance vessels in the hypertensive rat.

Thiophene systems. 9. Thienopyrimidinedione derivatives as potential antihypertensive agents.

A series of thieno[3,4-d]-, thieno[3,2-d]-, and thieno[2,3-d]pyrimidine-2,4-diones with (phenylpiperazinyl)alkyl substitution at N-3 have been synthesized and evaluated for antihypertensive effects in spontaneously hypertensive rats (SHR). These 49 compounds were compared to the vasodilator standards prazosin and the isosteric quinazoline-2,4-dione SGB 1534. Substitution at the 2-, 3-, or 4-position of the phenyl ring was examined, with that at the 2-position more potent than 4-substitution while the isomeric 3-substituted compounds were least potent. Neither alkylation nor acylation at the N-1 position improved the antihypertensive effects as compared to hydrogen. The three thienopyrimidine-2,4-diones (3-5) that contain a [(2-methoxyphenyl)piperazinyl]ethyl moiety at N-3 and hydrogen at N-1 were found to be potent oral antihypertensive agents in the SHR with doses (mg/kg, po) for reducing systolic blood pressure (SBP) by 50 mmHg (ED-50SBP) of 0.21, 0.19, and 1.0, respectively. The compounds 1-5 were further evaluated for alpha blocking potency by measuring the iv doses necessary to antagonize the phenylephrine pressor response by 50% (ED50) in the SHR. The ED50 values (micrograms/kg) are 10.4, 3.3, 1.7, 2.1, and 15.4, respectively. These results clearly show that all three thiophene systems have potent activity as antihypertensive agents and that 3 and 4 are more potent than 1 or 2 as alpha 1-antagonists in vivo.

Cardiotonic agents. Synthesis and inotropic activity of a series of isoquinolin-3-ol derivatives.

A series of isoquinolin-3-ol derivatives (II) was prepared as analogues of the clinical cardiotonic agent bemarinone (ORF 16600, I). Although in many respects the structural requirements for the cardiotonic activity of II are similar to those of bemarinone, certain differences between the series were noted. Our structure-activity studies show that II is less sensitive to alkoxy-substitution effects than is I, and more significantly, 4-substitution of II by alkyl groups, halogen, or alkanecarboxylic acid derivatives enhances cardiotonic activity in II in contrast to I, wherein analogous substitution eliminated activity. A linear correlation between contractile force (CF) increase and cyclic nucleotide phosphodiesterase fraction III (PDE-III) inhibition by the title compounds was determined. The isoquinoline derivatives were characteristically short-acting cardiotonic agents with good potency and selectivity.

Selective inhibition of 14 alpha-desmethyl sterol synthesis in Candida albicans by terconazole, a new triazole antimycotic.

Terconazole, a new broad spectrum antimycotic triazole derivative, has been shown to have potent activity against Candida albicans in vitro and to be effective in animal models of yeast infections. The present study explored a possible mechanism of anticandidal activity of terconazole. The compound inhibited production of 14 alpha-desmethyl sterols (e.g. ergosterol) in C. albicans at concentrations (IC50 = 3-6 x 10(-9) M) lower than those inhibiting the in-vitro growth of the yeast. There was concomitant accumulation of methylated sterols, (e.g. lanosterol), which are considered detrimental to normal yeast cell membrane function. Terconazole stimulated incorporation of 14C-acetate into triglycerides, but had no other effect on C. albicans lipid metabolism. At concentrations greater than or equal to 10(-6)M terconazole inhibited the oxidation of 14C-acetate into 14CO2 in C. albicans although the mechanism for this effect remains unclear. These data indicate that terconazole is a specific inhibitor of yeast C-14 desmethyl sterol production in C. albicans. Furthermore, terconazole reduced cytochrome P-450 levels in yeast microsomes at concentrations 10,000-fold below those at which it showed effects on rabbit liver microsomes. These data indicate a species specificity for the biochemical actions of terconazole. The C-14 alpha-desmethylase system in yeast cell membranes is cytochrome P-450 associated. Thus, terconazole, was a potent inhibitor of C-14 desmethyl sterol synthesis. This effect could contribute to the anticandidal activity of the drug.

Influence of amphotericin B on the transport of phosphate, sulphate and potassium ions across the human erythrocyte membrane.

Some effects of the clinically important fungicidal antibiotic amphotericin B on the transport of phosphate, sulphate and potassium ions across the membrane of the human erythrocyte were investigated. In general, amphotericin B inhibited the transport of the anions to about the same degree and stimulated the transport of the cation. At low concentrations, the inhibition of both phosphate and sulphate ion transport was concentration-dependent. A plateau was reached at 47 and 52% transport for phosphate and sulphate, respectively, beyond which no further inhibition was obtained. In contrast, the initial rate of potassium ion release from erythrocytes was stimulated. This effect was also concentration-dependent. The observed stimulatory effect on cation efflux was attributed to penetration of the antibiotic into the membrane of the erythrocyte, leading to the formation of specific channels. The inhibition of transport of anions, however, was attributed to alteration in the fluidity of the lipid bilayer consequent to channel formation.

Selective gastric antilesion properties of rioprostil, a prostaglandin E1 analog, in rats and dogs.

This paper characterizes the ability of rioprostil, a synthetic primary alcohol prostaglandin E1 analog, to inhibit gastric acid secretion and prevent experimentally induced gastric lesions in rats and dogs, and determines the selectivity (the separation in potency) for these effects. In 4-hr pylorus ligated rats, rioprostil inhibited gastric acid output when administered i.v., s.c., p.o. or intraduodenally, with ED50 values of 0.9, 1.8, 2.9 and 3.7 mg/kg, respectively. Rioprostil suppressed meal-stimulated acid output in Heidenhain pouch dogs and inhibited gastric acid output stimulated by tetragastrin, 2-deoxy-D-glucose, betazole or bethanechol in gastric fistula dogs with ED50 values of 7, 10, 16 and 17 micrograms/kg p.o., respectively. These values in dogs were not significantly different from each other, suggesting that the mechanism of the antisecretory effect of rioprostil is similar regardless of the secretagogue used. Rioprostil prevented ethanol induced gastric lesions in rats (ED50 = 1.5 micrograms/kg p.o.; 12.0 micrograms/kg s.c.) after a 30-min pretreatment. The 8-fold difference in potency between the p.o. and s.c. routes may reflect a local component in the antilesion mechanism of rioprostil. In dogs, rioprostil inhibited aspirin-induced gastric lesions with a p.o. ED50 of 1.6 micrograms/kg. Maximum antilesion activity in dogs for cimetidine or ranitidine was less than 50%, whereas rioprostil inhibited lesion formation by 100% without the appearance of side effects. Oral antilesion selectivity of rioprostil in rats (antisecretory ED50/antilesion ED50) was nearly 2000-fold using the optimum pretreatment time (30 min), and was 12-fold when the pretreatment time (4 hr) was the same as the duration of the antisecretory assay.(ABSTRACT TRUNCATED AT 250 WORDS)