Prolactin exerts hematopoietic growth-promoting effects in vivo and partially counteracts myelosuppression by azidothymidine

Prolactin (PRL) is a neuroendocrine hormone that influences immune and hema topoietic development, The mechanism of action of this hormone in vivo rema ins unclear; therefore, we assessed the effects of PRL on hematopoiesis in vivo and in vitro. Normal resting mice were treated with 0, 1, 10, or 100 m u g of recombinant human prolactin (rhPRL) for 4 consecutive days and eutha nized on the fifth day for analysis of myeloid and erythroid progenitors in the bone marrow and spleen. Both frequencies and absolute numbers of splen ic colony-forming unit granulocyte-macrophage (CFU-GM) and burst-forming un it-erythroid (BFU-e) were significantly increased in mice receiving rhPRL c ompared to the controls that had received saline only. Bone marrow cellular ities were not significantly affected by any dose of rhPRL, but the absolut e numbers and frequencies of bone marrow CFU-GM and BFU-e were augmented by rhPRL. These results suggest that rhPRL can promote hematopoiesis in vivo, Because rhPRL augments myeloid development in vivo, we examined the potent ial of the hormone to reverse the anemia and myelosuppression induced by az idothymidine (AZT), Mice were given rhPRL injections concurrent with 2.5 mg /mL AZT in drinking water, rhPRL partially restored hematocrits in the anim als after 2 weeks of treatment and increased CFU-GM and BFU-e in both splee ns and bone marrow, The experiments with AZT and rhPRL support the conclusi on that the hormone increases myeloid and erythroid progenitor numbers in v ivo, and they suggest that the hormone is clinically useful in reversing my elosuppression induced by AZT or other myeloablative therapies, (C) 1999 In ternational Society for Experimental Hematology, Published by Elsevier Scie nce Inc.