Parabiotic Demonstration of a Humoral Factor Affecting Megakaryocyte Size in S1/S1 d Mice 1

Summary

Parabiosis was done between S1/S1^d mice and their normal +/+ littermates and between pairs of +/+ mice. The purpose was to determine if S1/S1^d mice produced a substance that would stimulate megakaryocytopoiesis. It was found that +/+ mice attached to S1/S1^d mice showed macromegakaryocytosis suggesting that megakaryocytopoiesis was stimulated. Nonspecific findings in +/+ parabiotic pairs included a lesser degree of megakaryocyte macrocytosis. These findings did not appear to be due to growth of S1/S1^d stem cells in the +/+ parabionts. Radiation to S1/S1^d or +/+ bone marrow did not change the size of megakaryocytes. The results suggest that S1/S1^d mice produce a thrombopoietic substance even though they have a normal complement of circulating platelets.