Adenosine A(2A) receptors mediate cardiovascular responses to hypoxia in fetal sheep.
Nonselective adenosine (ADO) receptor antagonists block hypoxia-induced bradycardia and hypertension in fetal sheep. This study was designed to determine the ADO receptor subtype that is involved in these cardiovascular responses. In chronically catheterized fetal sheep (>0.8 term), fetal hypoxemia was induced by having the ewe breathe a hypoxic gas mixture (9% O(2)-3% CO(2)-88% N(2)) for 1 h. Intra-arterial infusion of ZM-241385, an antagonist highly selective for ADO A(2A) receptors, to eight fetuses during normoxia significantly increased mean arterial pressure (MAP) from 42.5 +/- 2.0 to 46.1 +/- 2.0 mmHg without altering heart rate (HR). Infusion of a selective antagonist of ADO A(1) receptors [1, 3-dipropyl-8-cyclopentylxanthine (DPCPX)] elevated MAP and HR only after the infusion was terminated, although administration of the vehicle for ZM-241385 or DPCPX had no effect on MAP or HR. Isocapnic hypoxia with infusion of DPCPX or the vehicle for DPCPX or ZM-241385 produced a transient fall in HR, a rise in MAP, and a decrease in plasma volume. In contrast, ADO A(2A) receptor blockade abolished the hypoxia-induced bradycardia and hypertension and blunted the decline in plasma volume. We conclude that fetal ADO A(2A) receptors: 1) modulate AP during normoxia, and 2) mediate cardiovascular responses during acute O(2) deficiency.
Koos
B J
BJ
Nicholas S. Assali Perinatal Research Laboratory, Departments of Obstetrics and Gynecology, Brain Research Institute, University of California at Los Angeles School of Medicine, Los Angeles, California 90095-1740, USA. bkoos@mednet.ucla.edu
Maeda
T
T
D000241:Adenosine / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D001784:Blood Gas Analysis; D001794:Blood Pressure; D005260:Female; D005311:Fetal Hypoxia / Q000503:physiopathology*; D006339:Heart Rate; D006863:Hydrogen-Ion Concentration; D010627:Phenethylamines / Q000494:pharmacology; D011247:Pregnancy; D058906:Purinergic P1 Receptor Agonists; D058915:Purinergic P1 Receptor Antagonists; D043705:Receptor, Adenosine A2A; D018047:Receptors, Purinergic P1 / Q000502:physiology*; D012756:Sheep; D014227:Triazines / Q000494:pharmacology; D014230:Triazoles / Q000494:pharmacology; D014970:Xanthines / Q000494:pharmacology
D010627:Phenethylamines; D058906:Purinergic P1 Receptor Agonists; D058915:Purinergic P1 Receptor Antagonists; D043705:Receptor, Adenosine A2A; D018047:Receptors, Purinergic P1; D014227:Triazines; D014230:Triazoles; D014970:Xanthines; C097270:ZM 241385; C061282:2-(4-(2-carboxyethyl)phenethylamino)-5'-N-ethylcarboxamidoadenosine; C048599:N(6)-cyclopentyladenosine; C051360:1,3-dipropyl-8-cyclopentylxanthine; D000241:Adenosine