Differential responses of pulmonary arteries and veins to histamine and 5-HT in lung explants of guinea-pigs.
1. The mechanisms by which histamine and 5-HT differentially contract pulmonary arteries and veins are unclear. In lung explants from 26 guinea-pigs, we compared responses of pulmonary arteries and vein to histamine, 5-HT and KCI, and examined potential determinants for the differential responses. Lungs were filled with agarose, sectioned into approximately 1 mm thick slices, and vascular luminal areas measured by image analysis. 2. Histamine and 5-HT produced a concentration-dependent constriction in arteries and veins, greater in the latter. KCl constricted arteries and veins equally. 3. The histamine H1 antagonist chlorpheniramine (10(-4) M) abolished contractions to histamine; the H2 antagonist cimetidine enhanced maximal responses and sensitivity of arteries and veins to histamine, and diminished the differences between their maximal responses; the NO synthase inhibitor Nomega-nitro-L-arginine (L-NOARG) increased the maximal responses of arteries and veins, and the differences between their responses; indomethacin had no effect. 4. Contractions to 5-HT were abolished in arteries and markedly reduced in veins by the 5-HT2 antagonist ketanserin (10(-4) M); L-NOARG potentiated the maximal responses of arteries but not of veins; indomethacin increased the maximal responses of arteries but reduced them in veins. 5. By morphometry, arteries had a greater medial thickness and luminal diameter than veins. 6. The data suggest that in guinea-pigs, H2 receptors are responsible for the differential contractile responses of pulmonary arteries and veins to histamine, whereas endothelium-derived vasoactive substances are responsible for their differential contractile responses to 5-HT.
Shi
W
W
Department of Pathology, McGill University, Montréal, QC, Canada.
Wang
C G
CG
Dandurand
R J
RJ
Eidelman
D H
DH
Michel
R P
RP
D000818:Animals; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006168:Guinea Pigs; D006632:Histamine / Q000494:pharmacology*; D006634:Histamine H1 Antagonists / Q000494:pharmacology; D006635:Histamine H2 Antagonists / Q000494:pharmacology; D007090:Image Interpretation, Computer-Assisted; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000033:anatomy & histology / Q000187:drug effects*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D011189:Potassium Chloride / Q000494:pharmacology; D011651:Pulmonary Artery / Q000033:anatomy & histology / Q000187:drug effects*; D011667:Pulmonary Veins / Q000033:anatomy & histology / Q000187:drug effects*; D012701:Serotonin / Q000494:pharmacology*
D016861:Cyclooxygenase Inhibitors; D004791:Enzyme Inhibitors; D006634:Histamine H1 Antagonists; D006635:Histamine H2 Antagonists; D012701:Serotonin; D011189:Potassium Chloride; D006632:Histamine; D019001:Nitric Oxide Synthase