Effect of age on the contractile response of the rat carotid artery in the presence of sympathetic drugs and L-NAME

For evaluating the age-related change in noradrenaline (NA)-induced contraction of isolated rat carotid artery (CA), the effect of α and β adrenoreceptor (AR) blockers and the role of nitric oxide (NO) were investigated.

METHODS

Concentration-response curves to NA (10-10-10-4 M) and α1 agonist phenylephrine (PE; 10-10-10-5 M) were constructed in isolated CA rings from young and middle-aged rats. The effects of nitric oxide synthase (NOS) inhibitor (L-NAME; 100 μM), α1-AR antagonist (prazosin; 0.1 μM), α2-AR antagonist (yohimbine; 0.1 μM) and β-AR antagonist (propranolol; 1 μM) on NA-induced contraction of isolated CA rings were examined. In CA rings preconstricted with NA, the responses to α2-AR agonist (clonidine; 10-7-10-5 M), β-AR agonist (isoprenaline; 10-8-10-5 M),), sodium nitroprusside (SNP; 10-9-10-5 M) were assessed.

RESULTS

The maximum contractile response of CA to NA and to PE was higher in younger than in middle-aged rats. Prazosin reduced the contractile response to NA in both groups, while propranolol, yohimbine and L-NAME did not affect NA-induced contraction in either of them. Clonidine, isoprenaline and SNP produced a dose-dependent vasorelaxation of CA rings, isoprenaline-induced vasodilatation was lower in middle-aged rats, while there was no difference in clonidine or SNP-induced relaxant effect between the two groups.

CONCLUSIONS

NA-induced contraction of isolated rat CA rings is decreased in old rats, this is related to α1-AR. β-AR mediated dilatation was compromised in middle-aged rats (endothelium-dependent). α2-AR and SNP-mediated dilator effect seems to be unchanged.

Modulation of metabolic and cardiac dysfunctions by insulin sensitizers and angiotensin receptor blocker in rat model of type 2 diabetes mellitus

The objective of this study was to investigate the modulation of metabolic dysfunctions, adiponectin levels, and cardiac dysfunctions of type 2 diabetes mellitus (T2DM) by a combination of the insulin sensitizer rosiglitazone and angiotensin receptor blocker telmisartan in an experimental rat model. Fifty male adult Sprague-Dawley rats were divided equally into 5 groups. Group I: fed normal chow; served as normal control group. Groups II-V: fed a high-fat diet (HFD) for 2 weeks, followed by injection of streptozotocin (STZ; 35 mg/kg) to create a model of T2DM. Group II: treated with vehicle. Group III: treated with rosiglitazone (4 mg/kg). Group IV: treated with telmisartan (5 mg/kg). Group V: treated with both agents. Untreated HFD-STZ rats showed elevated fasting blood glucose, insulin, homeostasis model assessment (HOMA) index, triglycerides (TGs), low-density lipoprotein cholesterol (LDL), and total serum cholesterol (TC), with a decrease in high-density lipoprotein cholesterol (HDL) and adiponectin levels (p < 0.001). Rosiglitazone exerted more improvement in all parameters than telmisartan did, and a combination of both did not augment the improvement further, except for TGs and adiponectin. For the isolated atrial study, a combination of rosiglitazone and telmisartan corrected the responses of the atria of HFD-STZ rats to the negative inotropic effect induced by adenosine better than either one did alone, whereas this combination, surprisingly, significantly attenuated the positive inotropic response to β-adrenoreceptor and α-adrenoreceptor agonists. In conclusion, rosiglitazone significantly improved the metabolic and cardiac dysfunctions in T2DM. Moreover, a combination of rosiglitazone and telmisartan offered more improvement in serum TGs and adiponectin, and restored the atrial inotropic response to adenosine. Surprisingly, this combination significantly attenuates the positive inotropic response to α1-adrenoreceptor and β-adrenoreceptor agonists.

Synthesis and structural assignment of certain pyrimido[1,2-alpha] benzimidazole derivatives

The pyrimido[1,2-alpha]benzimidazole derivatives compounds 1-8 were synthesized through cyclocondensation of 2-aminobenzimidazole with the appropriate benzsubstituted benzoylacetone by fusion at 150-170 degrees C for 5 h. Quaternary salts compounds 9-22 were obtained by quaternization of compounds 1-8 with dimethyl or diethyl sulfate and subsequent isolation as the relatively insoluble perchlorate salts. Assignment and confirmation of the structures of the newly synthesized compounds were based upon elemental microanalyses and other spectral evidence.

Utility of certain pi-acceptors for the spectrophotometric determination of some penicillins

Two simple and sensitive spectrophotometric methods are described for the determination of six penicillin derivatives. The methods are based on the reaction of these drugs as n-electron donors with either 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) or 7,7,8,8-tetracyanoquinodimethane (TCNQ) as pi-acceptors, to give a highly coloured radical anion. The coloured products are quantified spectrophotometrically at 460 and 842 nm for DDQ and TCNQ, respectively. The optimization of the different experimental conditions is described. The interference from streptomycin sulphate and common degradation products was also studied. The proposed methods were applied successfully to the determination of the different penicillins investigated, either in pure or dosage forms, with good accuracy and precision. The results were compared with those given by the official United States Pharmacopeial XXI method.

Tetrazolium salts in pharmaceutical analysis II: direct assay of diethylstilbestrol and diethylstilbestrol dipropionate

A convenient spectrophotometric determination of diethylstilbestrol and diethylstilbestrol dipropionate was developed involving their interaction with triphenyltetrazolium chloride at 50 degrees for 45 min and subsequent measurement of the formazan formed. The significance of extended conjugation within t,e 4,4'-stilbenediol molecule to induce the color reaction is documented. Ideal adherence of color absorption to Beer's law permitted accurate and precise determination of diethylstilbestrol and diethylstilbestrol dipropionate pure forms over the range of 2-22 microgram of diethylstilbestrol/ml. Application of the tetrazolium color reaction to the analysis of diethylstilbestrol dipropionate dosage forms was achieved without prior hydrolysis or extraction.

Improved spectrophotometric determination of antazoline

A simple, precise, and accurate spectrophotometric determination of antazoline salts was developed by improving the ceric sulfate procedure. Replacement of water with acetic acid for the preparation of all assay solutions permitted reproducible measurements of the chromogen that absorbed at 505 nm. An appreciable increase in color stability was attained by the controlled addition of perchloric acid to the ceric reagent prior to interaction with antazoline at room temperature. Evidence is provided to account for the oxidation of antazoline at the expense of a complex ceric species. Other 2-imidazolines or phenylephrine did not interfere with the investigated color reaction. In addition to the high value of the chromogen molar absorptivity, ideal adherence of color absorption to Beer's law permitted accurate and reproducible estimation of antazoline over the 1--10-microgram range. The procedure was applied to the analysis of different antazoline dosage forms.

Polarographic estimation of antazoline hydrochloride

The dc-polarographic investigation of antazoline hydrochloride in aqueous acidic media is described. Using potassium chloride-hydrochloric acid mixture as the supporting electrolyte (pH = 3.25), antazoline hydrochloride was electrochemically reduced at the dropping mercury electrode, with the production of two waves with E1/2 values of --1.35 and --1.65 V respectively. As revealed from the study of the effect of mercury column height, pH of the medium and concentration of the depolarizer, the polarographic reduction of the antazolinium cation is preceded by a catalytic H-wave. The diffusion-controlled nature of the electrode process permitted the quantitative determination of antazoline hydrochloride in concentrations down to 1.0 . 10(-4)M. Application of the presented procedure to the analysis of different dosage forms of the compound studied proved successful and compared favourably with official estimations of anatazoline salts. In view of its simplicity, accuracy and sensitivity, the presented polarographic method can be recommended for routine analysis of antazoline formulations.

Colorimetric determination of catecholamines by 2,3,5-triphenyltetrazolium chloride

A convenient spectrophotometric method was developed for the determination of epinephrine, levarterenol, isoproterenol, and methyldopa by reduction of 2,3,5-triphenyltetrazolium chloride and subsequent measurement of the formazan at 485 nm. With absolute alcohol as the solvent, maximum color absorption was attained in 30 min at 25 degrees in the presence of 0.1 N KOH. Evidence is provided to account for the reduction of the tetrazolium salt at the expense of the epinephrine catechol moiety. In addition to the considerably high values of the molar absorptivities of the chromogen formed, ideal adherence of the color absorption to the Beer-Lambert law permitted a sensitive microdetermination of these catecholamines in both pure forms and pharmaceutical formulations. The tetrazolium interaction was selective. No interference was encountered from common catecholamine antioxidants, adjuvants, or noncatechol degradation products.

Polarographic study of new antibacterial isoxazolium salts: 2,3-dialkyl-5-arylisoxazolium perchlorates

The polarographic reduction of new antibacterial 2,3-dialkyl-5-arylisoxazolium salts is described. The electrode process involves an irreversible two-electron transfer and is pH independent within the 6.0-10.0 range. In more acidic media, hydrogen waves are observed; at higher pH values, a chemical degradation of the isoxazolium salt proceeds. Values of the half-wave potential of the salts are dependent on the polar contribution of the 5-aryl substituents in terms of the Hammett equation. The in vitro minimum inhibitory concentrations of these compounds are best correlated with Hansch PI values.