The present invention provides methods and kits for mitigating radiation induced tissue damage, improving the effectiveness of radiation therapy, to support bone marrow transplantation, and promoting megakaryocyte production and mobilization and platelet production, each method comprising the administration of an effective amount of angiotensinogen, angiotensin I (AI), AI analogues, AI fragments and analogues thereof, angiotensin II (AII), AII analogues, AII fragments or analogues thereof or AII AT.sub.2 type 2 receptor agonists.