Expression of an erythropoietin-like gene in the trout

Cross-species Northern blot hybridization and radioimmunoassay have provided evidence for the expression of an erythropoietin (EPO)-like gene in the rainbow trout. The principal site of EPO-like mRNA and antigen expression in the adult trout appears to be the kidney which also acts as the major erythropoietic organ. The data suggest that a locally produced EPO-like factor may regulate renal erythropoiesis in bony fish and, furthermore, they identify a possible evolutionary origin for renal EPO production in mammals.