Plasma catecholamines in the hypoxaemic fetal rhesus monkey

Area of Science:

• Fetal Physiology
• Neuroendocrinology
• Perinatal Medicine

Background:

• The sympathoadrenal system plays a crucial role in fetal adaptation to stress.
• Oxygen deprivation (hypoxemia) is a significant stressor for the fetus.
• Understanding fetal stress responses is vital for perinatal care and outcomes.

Purpose of the Study:

• To investigate the fetal primate sympathoadrenal system's response to varying degrees of oxygen deprivation.
• To quantify changes in plasma catecholamine levels in fetal rhesus monkeys under induced hypoxemia.
• To compare the fetal response to maternal catecholamine levels during hypoxemia.

Main Methods:

• Chronic catheterization of fetal rhesus monkeys for blood sampling.
• Controlled maternal inhalation of low-oxygen mixtures (15%, 10%, 9%) to induce fetal hypoxemia.
• Radioenzymatic assay used to measure plasma catecholamine concentrations (norepinephrine, epinephrine, dopamine) in fetal and maternal blood.

Main Results:

• Fetal plasma norepinephrine and epinephrine concentrations significantly increased at all tested hypoxemia levels.
• Dopamine levels only rose at very low fetal oxygen tensions.
• Norepinephrine consistently exceeded epinephrine and dopamine levels under all conditions.
• A strong negative exponential correlation was observed between fetal oxygenation and plasma norepinephrine/epinephrine.
• Maternal catecholamines also increased but to a lesser extent than in the fetus.

Conclusions:

• The primate fetal sympathoadrenal system is highly sensitive to oxygen deprivation.
• Norepinephrine is the primary catecholamine released by the fetal primate in response to hypoxemia.
• The fetal response to hypoxemia is more pronounced than the maternal response.