ABSTRACT
Fluid cell membranes are the main barrier to drug absorption when diffusion limits uptake. Immobilized artificial membranes (IAMs) are solid phase models of fluid membranes that predicted oral drug absorption in mice for a homologous set of cephalosporins. IAMs also predicted drug permeability through Caco-2 cells. Since drug permeability in Caco-2 cells is known to correlate with the oral absorption of drugs in humans, IAMs may also model drug absorption in humans. IAM analysis is experimentally simple, and large-volume screening of experimental compounds for drug absorption is possible.
Subject(s)
Cell Membrane Permeability , Chromatography/methods , Membranes, Artificial , Pharmacokinetics , Animals , Biological Availability , Cell Line , Humans , Intestinal Absorption , MiceSubject(s)
Anti-Bacterial Agents/chemical synthesis , Anti-Bacterial Agents/pharmacology , Cephalosporins/chemical synthesis , Cephalosporins/pharmacology , Administration, Oral , Animals , Anti-Bacterial Agents/pharmacokinetics , Cefdinir , Cephalosporins/pharmacokinetics , Intestinal Absorption , Male , Mice , Mice, Inbred Strains , Microbial Sensitivity Tests , Rats , Rats, Sprague-DawleyABSTRACT
The structure-activity relationship among a series of novel pyrazolidinone antibacterial agents is described. Specifically, the effect of modification of the side chain attached to the nitrogen at C-7 was explored in an attempt to improve the potency and spectrum of activity. This approach was successful in identifying several compounds having good in vitro profiles. These top candidates were then evaluated for their activity in vivo, and their pharmacokinetic behavior in various animal models was explored. This information proved critical for the identification of candidates for clinical evaluation.
Subject(s)
Anti-Bacterial Agents/pharmacology , Anti-Bacterial Agents/pharmacokinetics , Bridged Bicyclo Compounds, Heterocyclic , Bridged Bicyclo Compounds/pharmacology , Bridged Bicyclo Compounds/pharmacokinetics , Pyrazoles/pharmacology , Pyrazoles/pharmacokinetics , Thiazoles/pharmacology , Thiazoles/pharmacokinetics , Animals , Anti-Bacterial Agents/chemistry , Bridged Bicyclo Compounds/chemistry , Gram-Negative Bacteria/drug effects , Gram-Positive Bacteria/drug effects , Half-Life , Macaca mulatta , Male , Mice , Mice, Inbred Strains , Microbial Sensitivity Tests , Pyrazoles/chemistry , Rats , Rats, Sprague-Dawley , Staphylococcus/drug effects , Structure-Activity Relationship , Thiazoles/chemistryABSTRACT
The synthesis and biological evaluation of novel 1-carba-1-dethiacephalosporins exhibiting activity against anaerobic pathogens are described. The nitrothiazole substituent was determined to be crucial to maintaining this activity. The pharmacokinetic parameters and initial toxicological profile of the lead compound are discussed.
Subject(s)
Bacteria, Anaerobic/drug effects , Cephalosporins/chemical synthesis , Cephalosporins/pharmacology , Animals , Cephalosporins/pharmacokinetics , Male , Rats , Rats, Sprague-DawleyABSTRACT
The synthesis and antimicrobial activity of several new 1-carba-1-dethiacephalosporins is described. The discovery of unique activity of some of the analogues against methicillin-resistant Staphylococcus aureus led to the development of a structure-activity relationship designed to optimize this activity. The results of this investigation along with the pharmacokinetic characteristics of select compounds are described.
Subject(s)
Anti-Bacterial Agents/chemical synthesis , Cephalosporins/chemical synthesis , Methicillin Resistance , Staphylococcus aureus/drug effects , Animals , Anti-Bacterial Agents/pharmacokinetics , Anti-Bacterial Agents/pharmacology , Blood Proteins/metabolism , Cephalosporins/pharmacokinetics , Cephalosporins/pharmacology , Half-Life , Humans , Macaca mulatta , Male , Mice , Mice, Inbred ICR , Microbial Sensitivity Tests , Rats , Rats, Sprague-Dawley , Structure-Activity RelationshipABSTRACT
The preparation and biological evaluation of a series of 7 beta-[2-(2-aminothiazol-4-yl)-2(Z)-methoximinoacetamido]cep halosporins, substituted at the 3'-position with monocyclic or bicyclic nitrogen-containing heterocycles are described. The resulting family of parenteral compounds displays a broad spectrum of antibacterial activity. Some compounds exhibit a similar level of Gram-negative activity to that of the "third-generation" cephalosporins with increased staphylococcal activity. The in vitro and in vivo antimicrobial activity, structure-activity relationships, beta-lactamase stability, and in vitro and in vivo pharmacological evaluations are presented.
Subject(s)
Cephalosporins/pharmacology , Animals , Blood Pressure/drug effects , Cephalosporins/metabolism , Cephalosporins/pharmacokinetics , Chemical Phenomena , Chemistry , Dogs , Enterobacter/drug effects , Escherichia coli/drug effects , Female , Guinea Pigs , Half-Life , Heart Rate/drug effects , Klebsiella pneumoniae/drug effects , Macaca mulatta , Male , Mice , Molecular Structure , Parasympatholytics/pharmacology , Pseudomonas aeruginosa/drug effects , Rats , Serratia marcescens/drug effects , Staphylococcus aureus/drug effects , Streptococcus/drug effects , Structure-Activity Relationship , beta-Lactamases/metabolismABSTRACT
A series of C(3)-cyclopropyl cephems and carbacephems has been prepared by palladium catalyzed addition of diazomethane to the corresponding C(3)-vinyl derivatives. The phenylglycyl cyclopropyl cephem derivatives exhibit better Gram-positive activity than cephalexin or cefaclor, while the aminothiazole oxime cyclopropyl cephem derivatives were not as active as the corresponding C(3)-vinyl cephems.
Subject(s)
Cephalosporins/chemical synthesis , Animals , Biological Availability , Cephalosporins/pharmacokinetics , Cephalosporins/pharmacology , Half-Life , Male , Mice , Microbial Sensitivity Tests , Molecular Structure , Rats , Rats, Inbred StrainsABSTRACT
A series of structurally unique 1-carba-1-dethiacephems is described. The structural stability of the 1-carba-1-dethiacephem nucleus was essential for the preparation of this series of 3-quaternary ammonium carbacephems. The known p-nitrobenzyl 7 beta-(phenoxyacetamido)- 3-[(trifluoromethyl)sulfonyl]oxy]-1-carba-1-dethia-3-cephem- 4-carboxylate served as both a quaternization substrate as well as a precursor to derivatives such as allyl 7 beta-[[2-[allyloxy)carbonyl]amino-4- thiazoly] (methoxyimino)acetyl]amino]-3-[(trifluoromethyl) sulfonyl] oxy]-1-carba-1-dethia-3-cephem-4-carboxylate. Quaternization of these enol triflates was accomplished either by dissolution in acetonitrile containing the base or by dissolution in the base, with or without warning to 50 degrees C. Bases nucleophilic enough to displace the triflate include a variety of substituted pyridines and N-methylimidazole. Deprotection then produced a very active series of 1-[7 beta-[(2-amino- 4-thiazolyl)(methoxyimino)acetyl]amino]-2-carboxy-8-oxo- 1-azabicyclo[4.2.0]oct-2-en-3-yl] quaternary ammonium hydroxide inner salts. These compounds were extremely potent antibacterials against a broad range of Gram-positive and -negative bacteria including constitutive cephalosporinase producers, such as Enterobacter cloacae. The compounds exhibit similar hydrolysis kinetics and pharmacokinetics to the analogous cephalosporin-3'-quaternary ammonium salts.
Subject(s)
Cephalosporins/pharmacology , Animals , Cephalosporins/chemical synthesis , Cephalosporins/pharmacokinetics , Chemical Phenomena , Chemistry , Gram-Negative Bacteria/drug effects , Gram-Positive Bacteria/drug effects , Models, Molecular , Rats , Structure-Activity RelationshipABSTRACT
Treatment of the plasma membrane H+-ATPase of Neurospora crassa with the arginine-specific reagents phenylglyoxal or 2,3-butanedione at 30 degrees C, pH 7.0, leads to a marked inhibition of ATPase activity. MgATP, the physiological substrate of the enzyme, protects against inactivation. MgADP, a competitive inhibitor of ATPase activity with a measured Ki of 0.11 mM, also protects, yielding calculated KD values of 0.125 and 0.115 mM in the presence of phenylglyoxal and 2,3-butanedione, respectively. The excellent agreement between Ki and KD values makes it likely that MgADP exerts its protective effect by binding to the catalytic site of the enzyme. Loss of activity follows pseudo-first order kinetics with respect to phenylglyoxal and 2,3-butanedione concentration, and double log plots of pseudo-first order rate constants versus reagent concentration yield slopes of 0.999 (phenylglyoxal) and 0.885 (2,3-butanedione), suggesting that the modification of one reactive site/mol of H+-ATPase is sufficient for inactivation. This stoichiometry has been confirmed by direct measurements of the incorporation of [14C]phenylglyoxal. Taken together, the results support the notion that one arginine residue, either located at the catalytic site or shielded by a conformational change upon nucleotide binding, plays an essential role in Neurospora H+-ATPase activity.
Subject(s)
Arginine , Neurospora crassa/enzymology , Neurospora/enzymology , Proton-Translocating ATPases/metabolism , Binding Sites , Diacetyl/pharmacology , Kinetics , Phenylglyoxal/metabolism , Phenylglyoxal/pharmacology , Protein Binding , Proton-Translocating ATPases/antagonists & inhibitors , Ribonucleotides/pharmacologyABSTRACT
The relationship between the transmembrane Na+ gradient and p-aminohippurate (PAH) transport was examined in isolated rat basolateral membrane vesicles. A 100 mM Na+ gradient (o leads to i) accelerated the influx of 50 microM [3H]PAH whereas similar gradients of choline+, K+, or Li+ did not. The sodium effect was not due to a diffusion potential. The Na+ gradient (o leads to i) decreased the apparent Michaelis constant for PAH from 0.167 +/- 0.016 to 0.054 +/- 0.016 mM and increased the maximum flux rate from 116.00 +/- 13.50 to 427.34 +/- 98.96 pmol/mg/min. An "overshoot" of [3H]PAH influx (159 +/- 4% of the equilibrium value) could be demonstrated only in the presence of a Na+ gradient (o leads to i) plus an opposing gradient of unlabeled PAH (i leads to o). These results suggest that PAH transport and the Na+ gradient are functionally related. A model for cellular uptake of PAH by a Na+ gradient-dependent anion exchange mechanism is presented.
Subject(s)
Aminohippuric Acids/metabolism , Ion Channels/physiology , Sodium/metabolism , p-Aminohippuric Acid/metabolism , Animals , Basement Membrane/metabolism , Biological Transport, Active , Cell Membrane Permeability , In Vitro Techniques , Kidney Tubules, Proximal/metabolism , Kinetics , Male , Membrane Potentials , Rats , Rats, Inbred Strains , Time FactorsABSTRACT
The cephalosporin antibiotics cephaloridine and cefazolin were examined for their effects on the transport of a prototype anion, [3H]p-aminohippurate (PAH) and a prototype cation, N1-[3H] methylnicotinamide (NMN) in basolateral membrane vesicles and brush border membrane vesicles (BBMV). Cefazolin inhibited transport of 50 microM PAH in both membranes and had no effect on transport of 50 microM NMN transport. Under identical conditions, cephaloridine, a zwitterion, inhibited PAH transport in both membranes and NMN transport in BBMV but not in basolateral membrane vesicles. Cephaloridine was less effective than cefazolin in inhibiting PAH transport in BBMV. The results demonstrate the organic transport systems in the basolateral membrane vesicles differ from those in the BBMV. Furthermore, a zwitterionic drug can interact with both systems in the BBMV. An explanation for the intracellular accumulation of cephaloridine is presented.