Developmental changes in atrial natriuretic factor content and localization of its messenger ribonucleic acid in ovine fetal heart

Abstract

The current study investigated the developmental changes in atrial natriuretic factor peptide content and messenger ribonucleic acid localization in the atria and ventricles of the ovine fetus throughout the second half of gestation. Ovine fetuses from 67 to 146 days' gestation (term 147 days) and newborn lambs were used for the study. Tissue atrial natriuretic factor contents were determined by radioimmunoassay, and atrial natriuretic factor messenger ribonucleic acid distribution was determined by in situ hybridization. In fetal atria, atrial natriuretic factor peptide levels were much greater than those in the ventricles. The levels in the atria increased with advancing gestation from 70 to 140 days, reflecting an increase in weight of the atrial chambers. A similar trend was not observed in the ventricles. In the atria, atrial natriuretic factor peptide content (per unit protein) reached high levels at 100 to 110 days' gestation; this was associated with an increase in level of atrial natriuretic factor gene expression. In the ventricles, atrial natriuretic factor peptide content and gene expression were very low throughout the second half of gestation, except for a peak in content that occurred at 100 days. Atrial natriuretic factor messenger ribonucleic acid abundance was much greater in the atria than in the ventricles in fetuses from 90 to 130 days' gestation. The distribution of atrial natriuretic factor messenger ribonucleic acid was homogeneous throughout the thickness of the atria and ventricles of the fetal heart. During the second half of gestation in the ovine fetus, the expression of atrial natriuretic factor messenger ribonucleic acid in the atria and ventricles paralleled the appearance of the peptide.