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Vasodilator tone in the llama fetus: the role of nitric oxide during normoxemia and hypoxemia
- Source :
- AMERICAN JOURNAL OF PHYSIOLOGY. REGULATORY, INTEGRATIVE AND COMPARATIVE PHYSIOLOGY, Artículos CONICYT, CONICYT Chile, instacron:CONICYT
- Publication Year :
- 2005
-
Abstract
- The fetal llama responds to hypoxemia, with a marked peripheral vasoconstriction but, unlike the sheep, with little or no increase in cerebral blood flow. We tested the hypothesis that the role of nitric oxide (NO) may be increased during hypoxemia in this species, to counterbalance a strong vasoconstrictor effect. Ten fetal llamas were operated under general anesthesia. Mean arterial pressure (MAP), heart rate, cardiac output, total vascular resistance, blood flows, and vascular resistances in cerebral, carotid and femoral vascular beds were determined. Two groups were studied, one with nitric oxide synthase (NOS) blocker NG-nitro-l-arginine methyl ester (l-NAME), and the other with 0.9% NaCl (control group), during normoxemia, hypoxemia, and recovery. During normoxemia, l-NAME produced an increase in fetal MAP and a rapid bradycardia. Cerebral, carotid, and femoral vascular resistance increased and blood flow decreased to carotid and femoral beds, while cerebral blood flow did not change significantly. However, during hypoxemia cerebral and carotid vascular resistance fell by 44% from its value in normoxemia after l-NAME, although femoral vascular resistance progressively increased and remained high during recovery. We conclude that in the llama fetus: 1) NO has an important role in maintaining a vasodilator tone during both normoxemia and hypoxemia in cerebral and femoral vascular beds and 2) during hypoxemia, NOS blockade unmasked the action of other vasodilator agents that contribute, with nitric oxide, to preserving blood flow and oxygen delivery to the tissues.
- Subjects :
- medicine.medical_specialty
Physiology
Vasodilation
Blood Pressure
Nitric Oxide
Hypoxemia
Nitric oxide
chemistry.chemical_compound
Fetal Heart
Fetus
Heart Rate
Pregnancy
Physiology (medical)
Internal medicine
Medicine
Animals
Cardiac Output
Hypoxia
business.industry
Hypoxia (medical)
Fetal Blood
Femoral Artery
medicine.anatomical_structure
Carotid Arteries
chemistry
Anesthesia
Cerebrovascular Circulation
Circulatory system
Vascular resistance
Cardiology
Female
Vascular Resistance
Gases
medicine.symptom
business
Camelids, New World
Vasoconstriction
Blood vessel
Subjects
Details
- ISSN :
- 03636119
- Volume :
- 289
- Issue :
- 3
- Database :
- OpenAIRE
- Journal :
- American journal of physiology. Regulatory, integrative and comparative physiology
- Accession number :
- edsair.doi.dedup.....c1bb4d3c744dee35c190c9bee3d8a351