Adenosine mediates hypoxic release of arginine vasopressin in fetal sheep.
The effects of adenosine on plasma arginine vasopressin (AVP) concentrations were determined in chronically catheterized fetal sheep (> 0.8 term). Infusion of adenosine [0.35 +/- 0.01 (SE) mg.min-1.kg-1] into the inferior vena cava of six fetuses caused a transient fall in arterial PO2 (by approximately 3 Torr), a slight reduction in arterial pH, and a 5- to 6-mmHg decrease in diastolic pressure without significantly affecting systolic or mean arterial values. A lower rate of infusion (0.19 +/- 0.01 mg.min-1 x kg-1) in five fetuses had virtually no effect on arterial blood gases, pH, or arterial pressures. Both the low- and high-dose adenosine infusions significantly increased fetal plasma AVP concentrations (1.7 +/- 0.2 to 25 +/- 7 pg/ml and 1.6 +/- 0.1 to 54 +/- 8 pg/ml, respectively). Intravenous infusion of papaverine lowered fetal diastolic and mean arterial pressures by approximately 8 mmHg but had no significant effect on plasma levels of AVP. During an hour of isocapnic hypoxia (arterial PO2 12-13 Torr), fetal plasma AVP levels increased from 1.7 +/- 0.2 to 40 +/- 6 pg/ml. Intra-arterial infusion of the adenosine receptor antagonist 8-(p-sulfophenyl)-theophylline significantly blunted the hypoxia-induced rise in plasma AVP concentrations to a maximum mean level of 11 +/- 6 pg/ml. These results indicate that 1) adenosine causes a dose-dependent increase in plasma AVP concentrations and 2) a hypoxia-induced rise in fetal adenosine levels triggers vasopressin release.
Koos
B J
BJ
Department of Obstetrics and Gynecology, Nicholas S. Assali Perinatal Research Laboratory, University of California at Los Angeles 90024.
Mason
B A
BA
Ervin
M G
MG
D000241:Adenosine / Q000502:physiology*; D000818:Animals; D001127:Arginine Vasopressin / Q000097:blood / Q000378:metabolism*; D001794:Blood Pressure / Q000187:drug effects; D005333:Fetus / Q000378:metabolism*; D005740:Gases / Q000097:blood; D006339:Heart Rate / Q000187:drug effects; D006863:Hydrogen-Ion Concentration; D000860:Hypoxia / Q000097:blood / Q000378:metabolism*; D010208:Papaverine / Q000494:pharmacology; D058915:Purinergic P1 Receptor Antagonists; D012756:Sheep; D013806:Theophylline / Q000031:analogs & derivatives / Q000494:pharmacology
D005740:Gases; D058915:Purinergic P1 Receptor Antagonists; D001127:Arginine Vasopressin; C031433:8-(4-sulfophenyl)theophylline; D013806:Theophylline; D010208:Papaverine; D000241:Adenosine