A study of the histamine H2-receptor mediating relaxation of the parenchymal lung strip preparation of the guinea-pig.
The relaxation produced by several H2-receptor agonists and forskolin was investigated on strips of guinea-pig lung parenchyma. Dimparit, 1 microM to 10 mM, 4-methyl histamine, 0.5 microM to 100 microM and impromidine, 10 nM to 1 microM, had no effect on the tone of the unstimulated strips of lung parenchyma but caused a dose-dependent relaxation of strips that were contracted by 2-pyridylethylamine (2-PEA), 15 microM. Forskolin, 10 nM to 4 microM, produced a dose-dependent relaxation of both the stimulated and unstimulated lung strips. The muscarinic antagonist atropine, 1 microM, and the beta 2-adrenoceptor antagonist propranolol, 10 microM, had no effect on the dose-response curve for dimaprit-induced relaxation of the lung strip. The dose-response curve for dimaprit was shifted to the right in a dose-dependent manner by increasing concentrations of a variety of H2-antagonists. Schild plots produced a straight line for all the H2-antagonists with slopes not significantly different from unity. The equilibrium dissociation constants for the H2-antagonists on the lung strip preparation were similar to those previously reported for inhibition of the chronotropic activity of histamine on guinea-pig right atria and inhibition of [3H]-tiotidine binding to homogenates of guinea-pig lung parenchyma.
Foreman
J C
JC
Rising
T J
TJ
Webber
S E
SE
D000818:Animals; D001285:Atropine / Q000494:pharmacology; D005576:Colforsin / Q000494:pharmacology; D017259:Dimaprit; D005260:Female; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008168:Lung / Q000187:drug effects; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects*; D011433:Propranolol / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D011968:Receptors, Histamine / Q000502:physiology*; D011970:Receptors, Histamine H2 / Q000502:physiology*; D013890:Thiourea / Q000494:pharmacology
D011725:Pyridines; D011968:Receptors, Histamine; D011970:Receptors, Histamine H2; D005576:Colforsin; D001285:Atropine; D011433:Propranolol; C006183:2-(2-aminoethyl)pyridine; D013890:Thiourea; D017259:Dimaprit