Sustained fetal pulmonary vasodilation with prolonged atrial natriuretic factor and GMP infusions.
To study mechanisms of vasodilation and factors that maintain high pulmonary vascular resistance in utero, we measured changes in blood flow and the pressure-flow relationship of the pulmonary circulation during prolonged exposures to direct-acting guanosine 3',5'-cyclic monophosphate (cGMP) vasodilators, atrial natriuretic factor (ANF), and 8-bromoguanosine 3',5'-cyclic monophosphate (8-BrcGMP) and compared hemodynamic responses with other vasodilator stimuli in chronically prepared fetal lambs. The fetus was treated with 2 h of intrapulmonary infusions of ANF (0.15 micrograms/min), 8-BrcGMP (50 micrograms/min), prostaglandin D2 (PGD2, 0.4 micrograms/min), or acetylcholine (ACh, 1.5 micrograms/min) or increases in fetal Po2. Despite continued exposure to increased Po2, PGD2, and ACh, elevations of pulmonary blood flow and slopes of the pressure-flow relationship were not sustained, with both significantly decreased at 2 h from peak values. In contrast, pulmonary blood flow and pressure-flow slopes remained increased throughout 2 h of exposures to ANF and 8-BrcGMP. Adenosine 3',5'-cyclic monophosphate caused less change in blood flow than 8-BrcGMP within the dose range studied. We conclude that unlike other stimuli, direct-acting cGMP vasodilators are able to sustain vascular relaxation of the fetal pulmonary circulation.
Abman
S H
SH
Department of Pediatrics, University of Colorado School of Medicine, Denver 80262.
Accurso
F J
FJ
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D009320:Atrial Natriuretic Factor / Q000008:administration & dosage / Q000494:pharmacology*; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D006152:Cyclic GMP / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005260:Female; D005333:Fetus / Q000187:drug effects / Q000502:physiology*; D006439:Hemodynamics / Q000187:drug effects / Q000502:physiology; D007261:Infusions, Intra-Arterial; D008168:Lung / Q000098:blood supply* / Q000196:embryology / Q000502:physiology; D010100:Oxygen / Q000494:pharmacology; D011247:Pregnancy; D015230:Prostaglandin D2 / Q000494:pharmacology; D012039:Regional Blood Flow / Q000187:drug effects; D012756:Sheep / Q000502:physiology*; D013997:Time Factors; D014664:Vasodilation / Q000187:drug effects* / Q000502:physiology
C016276:8-bromocyclic GMP; D009320:Atrial Natriuretic Factor; D006152:Cyclic GMP; D000109:Acetylcholine; D015230:Prostaglandin D2; D010100:Oxygen