Evidence that the renin decrease during hypoxia is adenosine mediated in conscious dogs.
This study investigated whether adenosine mediates the decrease in plasma renin activity (PRA) during acute hypoxia. Eight chronically tracheotomized, conscious beagle dogs were kept under standardized environmental conditions and received a low-sodium diet (0.5 mmol.kg body wt(-1).day(-1)). During the experiments, the dogs were breathing spontaneously via a ventilator circuit: first hour, normoxia (21% inspiratory concentration of O(2)); second and third hours, hypoxia (10% inspiratory concentration of O(2)). Each of the eight dogs was studied twice in randomized order in control and theophylline experiments. In theophylline experiments, theophylline, an A(1)-receptor antagonist, was infused intravenously during hypoxia (loading dose: 3 mg/kg within 30 min, maintenance: 0.5 mg. kg(-1). h(-1)). In theophylline experiments, PRA (5.9 +/- 0.8 ng ANG I. ml(-1). h(-1)) and ANG II plasma concentration (15.9 +/- 2.3 pg/ml) did not decrease during hypoxia, whereas plasma aldosterone concentration decreased from 277 +/- 63 to 132 +/- 23 pg/ml (P < 0.05). In control experiments, PRA decreased from 6.8 +/- 0.8 during normoxia to 3.0 +/- 0.5 ng ANG I. ml(-1). h(-1) during hypoxia, ANG II decreased from 13.3 +/- 1.9 to 7.3 +/- 1.9 pg/ml, and plasma aldosterone concentration decreased from 316 +/- 50 to 70 +/- 13 pg/ml (P < 0.05). Thus infusion of the adenosine receptor antagonist theophylline inhibited the suppression of the renin-angiotensin system during acute hypoxia. The decrease in aldosterone occurred independently and is apparently directly related to hypoxia. In conclusion, it is likely that adenosine mediates the decrease in PRA during acute hypoxia in conscious dogs.
Höhne
C
C
Experimental Anesthesia, Clinics of Anesthesiology and Operative Intensive Care Medicine, Charité, D-13353 Berlin, Germany.
Krebs
M O
MO
Boemke
W
W
Arntz
E
E
Kaczmarczyk
G
G
D000208:Acute Disease; D000241:Adenosine / Q000502:physiology; D000450:Aldosterone / Q000097:blood; D000803:Angiotensin I / Q000097:blood; D000804:Angiotensin II / Q000097:blood; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002245:Carbon Dioxide / Q000097:blood; D003243:Consciousness; D004039:Diet, Sodium-Restricted; D004285:Dogs; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects / Q000502:physiology*; D000860:Hypoxia / Q000097:blood / Q000503:physiopathology*; D010100:Oxygen / Q000097:blood; D010313:Partial Pressure; D011188:Potassium / Q000097:blood; D058915:Purinergic P1 Receptor Antagonists; D012083:Renin / Q000097:blood*; D012084:Renin-Angiotensin System / Q000187:drug effects / Q000502:physiology*; D013806:Theophylline / Q000008:administration & dosage / Q000494:pharmacology*
D058915:Purinergic P1 Receptor Antagonists; D000804:Angiotensin II; D002245:Carbon Dioxide; D000450:Aldosterone; D000803:Angiotensin I; D013806:Theophylline; D012083:Renin; D000241:Adenosine; D011188:Potassium; D010100:Oxygen