title: Effects of physiological aging on cardiac electrophysiology in perfused Fischer 344 rat hearts.
abstract: Aging effects on heart rate and atrioventricular (AV) conduction were studied in Langendorff-perfused hearts from 18 mature (4-6 mo), 12 middle-aged (12-14 mo), and 18 senescent (24-26 mo) Fischer 344 rats. Heart rate decreased with increasing age from 218 +/- 18 in mature to 196 +/- 27 (mean +/- SD) beats/min in middle-aged rats to 183 +/- 22 beats/min in senescent rats (analysis of variance, P less than 0.001). Spontaneous AV conduction time increased from 43 +/- 7 to 49 +/- 5 to 62 +/- 9 ms with aging (P less than 0.0001). Paced AV conduction time also lengthened with aging, and AV Wenckebach block cycle length increased from 122 +/- 10 to 133 +/- 9 to 152 +/- 16 ms (P less than 0.005). Intra-atrial conduction time was unaffected by age. Age differences in heart rate and AV conduction responses to isoproterenol (0.5 x 10(-9) to 1 x 10(-7) M) were noted with greater sensitivity at lower doses in hearts from younger rats. In separate experiments, 18 mature and 19 senescent Fischer 344 rats received reserpine (0.25 mg.kg-1.day-1 ip) for 6 days before study. Age differences in heart rate and AV conduction persisted (P less than 0.0001). Histopathological examination of AV nodal and His-bundle tissues in three hearts from each age group showed increased intercellular collagen with advancing age.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Medicine, University of California, San Francisco 94143.
authors.forename: O
authors.initials: O
authors.lastname: Schmidlin
authors.forename: S
authors.initials: S
authors.lastname: Bharati
authors.forename: M
authors.initials: M
authors.lastname: Lev
authors.forename: J B
authors.initials: JB
authors.lastname: Schwartz
mesh_terms: D000375:Aging / Q000502:physiology*; D000818:Animals; D001283:Atrioventricular Node / Q000473:pathology; D002036:Bundle of His / Q000473:pathology; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D006321:Heart / Q000187:drug effects / Q000502:physiology*; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D010477:Perfusion; D051381:Rats; D011916:Rats, Inbred F344 / Q000502:physiology*; D012110:Reserpine / Q000494:pharmacology
chemical_list: D012110:Reserpine; D007545:Isoproterenol