THE DISTRIBUTION AND CLEARANCES OF HORMONES AND METABOLITES IN THE CIRCULATION OF THE FOETAL SHEEP

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Abstract
Plasma hormone and metabolite concentrations were measured in the plasma of blood collected simultaneously from the femoral artery, umbilical vein and carotid artery of the exteriorized fetal sheep. The concentration of vasopressin and catecholamines was consistently lower and that of glucose, lactate and corticosteroids consistently higher in the umbilical vein compared with the femoral artery. ACTH concentrations showed no consistent pattern and fluctuated widely at each site, but during synacthen infusion the concentration in the umbilical vein was consistently lower than in the femoral artery. For corticosteroids the concentration in the carotid artery was much lower than that in the umbilical vein; the converse was true for catecholamines. Concentrations in the carotid and femoral artery were similar for all compounds investigated. The placenta was a major site of vasopressin, catecholamine and ACTH clearance and of glucose, lactate and corticosteroid production. The fetal liver was probably a major site of corticosteroid and catecholamine clearance.