Erythropoietin in pigs: Perinatal changes, stimulatory effect of IRON and characterization of the erythropoietin gene

The rapid growth of pigs in the late foetal and early neonatal periods puts a heavy demand on their hematopoietic system. Arterial p02 in pig foetuses is low. Nevertheless, piglets are born with a low erythropoietin (EPO) activity. During the first 24 h after birth there is, however, a large increase in EPO activity, which then returns to low values after 7 to 10 days. Similar changes have been observed in newborn lambs. In piglets which are not supplemented with iron, a serious anemia develops during their first two weeks of life. Injection of iron results in a substantial increase in EPO activity during the next 24 h. An increase in EPO activity upon iron treatment has also been demonstrated in mice. As a first step towards the elucidation of the mechanisms behind the observed changes in EPO activity, the porcine EPO gene has been isolated and characterized. The gene with its promotor as well as 5' and 3' regions have been sequenced, and the gene structure determined. A repetitive element has been identified in the 5' region, and a putative oxygen-regulated transcriptional enhancer in the 3' region. Fluorescent in situ hybridization has assigned the porcine EPO gene to chromosome 3p15-p16. In order to develop a homologous assay for porcine EPO, antibodies have been raised against a synthetic peptide that upon analyses of the deduced porcine protein sequence has been identified as highly antigenic. A competitive RT-PCR method is being used for quantitation of EPO mRNA expression in response to iron treatment.