RESUMO
Multiple injections of dobutamine, a selective adrenergic beta-1 receptor agonist, or isoproterenol, a nonselective beta receptor agonist, produced significant dose-dependent enlargement of the submandibular glands of male rats. The glandular enlargement induced by dobutamine or isoproterenol was characterized by significant increases in glandular protein and nucleic acid content and a marked increase in the RNA/DNA ratio. Metoprolol, a selective beta-1 receptor antagonist, significantly inhibited the glandular enlargement induced by dobutamine or isoproterenol and produced a parallel shift in the isoproterenol dose-response curve. Metoprolol also inhibited the increased protein and nucleic acid content induced by dobutamine or isoproterenol. Multiple injections of selective adrenergic beta-2 receptor agonists, terbutaline, fenoterol or salmefamole, failed to produce submandibular gland enlargement. These results indicate that adrenergic beta-1 receptors mediate submandibular gland hypertrophy in the rat.
Assuntos
Receptores Adrenérgicos beta/fisiologia , Receptores Adrenérgicos/fisiologia , Glândula Submandibular/patologia , Agonistas Adrenérgicos beta/farmacologia , Animais , Cardiomegalia/induzido quimicamente , Relação Dose-Resposta a Droga , Hipertrofia/induzido quimicamente , Hipertrofia/fisiopatologia , Isoproterenol/farmacologia , Masculino , Metoprolol/farmacologia , Ratos , Glândula Submandibular/efeitos dos fármacosRESUMO
The metabolism of branched-chain amino acids, branched-chain acyl derivatives, d-glucose, l-glutamate, and Mueller-Hinton medium was investigated to determine their effects on the growth, lipid composition, and antibiotic susceptibility of Pseudomonas aeruginosa. The unsaturated fatty acid content of the readily extractable lipids was altered by growth on selected branched-chain amino acids and their acyl derivatives. Bacteria grown on branched-chain acyl derivatives became more susceptible to polymyxin B and colistin. The effect acyl derivatives had on increasing susceptibility was also manifest in mixed media which contained both an acyl derivative and a carbon source which did not increase susceptibility. Growth on branched-chain amino acids gave mixed results which were dependent on a number of factors, including unique manifestations of individual amino acids, growth conditions, and availability of other carbon sources. The cultural conditions which altered susceptibility to polymyxin antibiotics did not correlate with similar effects on susceptibility to carbenicillin and gentamicin. An adaptive resistance to polymyxin B was observed when the sole carbon source was d-glucose or l-glutamate.