( The present investigation was done in the department of Physiology, Faculty of Veterinary Medicine, Zagazig Atomic Power Do~d:iCairo U A R frem July 1980 to December,’ 1982•1155 irrunature mioe were usec males, females and virigins (treated with .hormonThe present study was conduc t ed on ~!~:5 inunature mice were given intraperitonea1ly a permissible dose level of the radioactive calcium 45 ca (0.05 ml containing 0.11 millicuri). After one week, animals were grouped into three groups according to theirThe first five animals of each subdivision were intrape- r1toneally injected with 10 Ug prolactin solution, the second ~;a.nimals •• re received 59 Ug prolactin. the