title: Influence of age on relaxation of rat blood vessels to atriopeptin II.
abstract: The ability of atriopeptin II to relax isolated ring segments of the thoracic aorta and renal, mesenteric and carotid arteries was studied in Fischer 344 rats aged 6, 12, 20 and 24 to 27 months. Vessels were precontracted with norepinephrine (aorta, mesenteric and carotid arteries) or serotonin (renal artery) in concentrations that produced approximately 50% of the maximal contractile response. Agonist concentrations used and magnitude of induced tone did not change with age, except in the carotid artery, where tone induced in vessels from the oldest group of animals was significantly greater. Thus it was possible to obtain contractile responses that were relatively stable with age in order to test the effect of age on relaxation responses effectively. There were significant differences in sensitivity to atriopeptin II and maximum relaxation among the vessels studied when comparisons were made within a single age group. Thus the thoracic aorta and carotid artery were more sensitive to atriopeptin II and had greater maximum relaxation responses than the renal and mesenteric arteries. In terms of the influence of age, for the most part neither sensitivity to atriopeptin II nor maximum relaxation response changed with age. However, there were some exceptions. Particularly in the thoracic aorta at several concentrations of atriopeptin II, relaxation in vessels from animals 12 months of age was significantly greater than in the other age groups. This difference is most likely due to an effect of maturation, as there was no further alteration in atriopeptin sensitivity into senescence.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000375:Aging; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects; D001158:Arteries / Q000187:drug effects* / Q000254:growth & development; D009320:Atrial Natriuretic Factor / Q000494:pharmacology*; D002339:Carotid Arteries / Q000187:drug effects; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D008638:Mesenteric Arteries / Q000187:drug effects; D009638:Norepinephrine / Q000494:pharmacology; D051381:Rats; D011916:Rats, Inbred F344; D012077:Renal Artery / Q000187:drug effects; D012701:Serotonin / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects*
chemical_list: D012701:Serotonin; D009320:Atrial Natriuretic Factor; D009638:Norepinephrine