GENE-EXPRESSION OF ATRIAL-NATRIURETIC-FACTOR IN OVINE FETAL HEART DURING DEVELOPMENT

OBJECTIVE: The present study quantified the abundance of atrial natriu retic factor (ANF) messenger RNA (mRNA) and determined the development al pattern of ANF gene expression in the four cardiac chambers of the ovine fetus during the last two-thirds of gestation. METHODS: Twenty-o ne fetuses from 13 time-dated pregnant ewes at gestational ages of 60- 145 days were used for this study. Total RNA from fetal atria and vent ricles was extracted and ANF mRNA was analyzed by Northern blotting. T he ANF mRNA signal was quantified by light densitometry. The abundance of ANF mRNA in the cardiac chambers across gestational ages was analy zed by linear regression analysis and one-way analysis of variance. RE SULTS: Atrial natriuretic factor mRNA was much more abundant in the at ria than in the ventricles of all fetuses at each gestational age stud ied. Atrial ANF mRNA levels were lowest in the younger fetuses at 60 d ays and increased with advancing gestation. Ventricular ANF mRNA level s were highest in fetuses at 60 days and decreased to almost nondetect able levels tlear term. No difference in ANF mRNA abundance was noted between the right and left atria or the right and left ventricles at e ach gestational age. CONCLUSION: A developmental pattern of ANF gene e xpression is demonstrated irt tire ovine fetal heart during the last t wo-thirds of gestation. This pattern shows that atrial ANF mRNA abunda nce increases while ventricular abundance decreases as the fetus matur es. Expression of the ANF gene in the fetal period may be regulated de velopmentally or induced by cardiovascular changes in utero.