Catecholamine synthetic capacity and dopamine receptors in fetal rat lung

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Catecholamine (CA) synthetic capacity in fetal rat lung was cxamined on Day 20 of gestation. Three common CAs were present in the fetal rat lung. But their proportions differed from those in the adrenal gland, brain, blood, and amniotic fluid. To confirm the capacity of the fetal rat lung to synthesize CA,L-dopa was injected into pregnant rats, and CAs in the lungs of the fetuses of these rats were measured. The concentrations of all three CAs were increased significantly as compared with those in the lungs of fetuses from control rats. Immunohistochemical technique served to localize the CA synthetic enzyme, aromatic-L-amino acid decarboxylase, in the lung. The concentration of CAs in the lungs of growth-retarded rat fetuses prepared by the Wigglesworth method was higher than in the lungs of normal fetuses. Thus, it appeared that CAs exist in the fetal rat lung, and that fetal lung can synthesize all CAs. Findings in growth-retarded fetuses suggest that CA content in the fetal lung may be altered under conditions of chronic hypoxia.