title: Transient hypercapnic stress causes exaggerated and prolonged elevation of cardiac and renal interstitial norepinephrine levels in conscious hypertensive rats.
abstract: The responses of sympathetic nerve activity to transient stress can be exaggerated in salt-sensitive (SS), hypertensive subjects. Cardiac and renal interstitial norepinephrine (iNE) levels during and after transient hypercapnia were investigated in conscious SS rats. Dahl SS and salt-resistant (SR) 6-wk-old rats were fed a high-salt diet, and at 12 wk iNE levels in the heart and kidney were determined using microdialysis with probes inserted in the left ventricular (LV) wall and kidney. A telemetry system determined blood pressure and heart rate (HR) in separate animals. After recovery from the operation, data were collected before, during, and after exposure to normoxic 10% CO(2) for 25 min under unanesthetized conditions. The plasma NE concentrations at baseline did not differ between the two strains. Both cardiac and renal iNE levels were much higher in SS rats than in SR rats at baseline as well as during hypercapnic stress. After stress, the markedly increased iNE levels of SS rats were prolonged in the LV as well as in the kidney. During hypercapnic stress, HR decreased in both SS and SR rats, while sudden increases in HR immediately after the withdrawal from stress were followed by its slower reduction in SS rats compared with SR rats. In conclusion, transient hypercapnic stress causes exaggerated and prolonged elevation of iNE levels in the heart as well as in kidneys of SS animals.
authors.affiliation: The Second Dept. of Internal Medicine, Graduate School of Medicine, Univ. of Toyama, 2630 Sugitani, Toyama 930-0194, Japan.
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Sobajima
authors.forename: Takashi
authors.initials: T
authors.lastname: Nozawa
authors.forename: Teruo
authors.initials: T
authors.lastname: Nakadate
authors.forename: Takuya
authors.initials: T
authors.lastname: Shida
authors.forename: Takashi
authors.initials: T
authors.lastname: Ohori
authors.forename: Takayuki
authors.initials: T
authors.lastname: Suzuki
authors.forename: Akira
authors.initials: A
authors.lastname: Matsuki
authors.forename: Tadakazu
authors.initials: T
authors.lastname: Hirai
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Inoue
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000502:physiology; D003243:Consciousness / Q000502:physiology; D004195:Disease Models, Animal; D006339:Heart Rate / Q000502:physiology; D006935:Hypercapnia / Q000378:metabolism*; D006973:Hypertension / Q000378:metabolism*; D007668:Kidney / Q000378:metabolism*; D017551:Microdialysis; D009206:Myocardium / Q000378:metabolism*; D009638:Norepinephrine / Q000378:metabolism*; D051381:Rats; D020303:Rats, Inbred Dahl; D056152:Respiratory Rate / Q000502:physiology; D014474:Unconsciousness / Q000378:metabolism / Q000503:physiopathology
chemical_list: D009638:Norepinephrine