Influence of melatonin on bovine pulmonary vascular and bronchial airway smooth muscle tone.
The influence of melatonin on tension of isolated bovine pulmonary vascular and bronchial smooth muscle rings were examined in these experiments. Melatonin caused a dose-dependent relaxation of precontracted (30 mM KCl) pulmonary artery and vein, although the effect is greater in arterial smooth muscle. This relaxant response was blocked by preincubating vessels with antagonists of vasoactive intestinal peptide or Substance P. In bronchial smooth muscle, melatonin caused a small contractile response. These experiments demonstrate that in response to melatonin the pulmonary vasculature relaxes, while in airway smooth muscle the reverse, constriction, occurs. It is hypothesized that nocturnal exaggeration of asthma may, in part, be due to changes in circulating levels of melatonin.
Weekley
L B
LB
Division of Comparative Medicine, University of Texas Southwestern Medical School, Dallas 75235-9037, USA.
D000818:Animals; D001980:Bronchi / Q000187:drug effects*; D002417:Cattle; D066298:In Vitro Techniques; D008297:Male; D008550:Melatonin / Q000494:pharmacology*; D009129:Muscle Tonus / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects; D011651:Pulmonary Artery / Q000187:drug effects*; D011667:Pulmonary Veins / Q000187:drug effects*; D013373:Substance P / Q000494:pharmacology; D014660:Vasoactive Intestinal Peptide / Q000494:pharmacology
D013373:Substance P; D014660:Vasoactive Intestinal Peptide; D008550:Melatonin