Blood Platelet Production and Red Cell Leakage to Lymph during Thrombocytopenia

Previous investigations have shown that a vascular wall defect will usually, but not always, develop during irradiation‐induced thrombocytopenia. This phenomenon has been further examined by observing the content of red cells in ear lymph in rabbits 9–10 days after exposure to a sublethal dose (660 rads) of whole body irradiation during which the ears were shielded. Increased number of red cells in the ear lymph was found in about 2/3 of 51 such thrombocytopenic animals (< 35,000 platelets/μl blood). When a small dose of platelet antiserum was given to some of the remaining and similarly thrombocytopenic animals, a marked increase in the red cell content of the ear lymph also appeared in these cases. Results achieved in additional experiments with 660 rads exposure indicated that some production of blood platelets remained even during the days with most marked thrombocytopenia. Another group of animals was therefore exposed to the (lethal) dose of 1,300 rads which eliminated platelet production completely. These animals invariably developed an abnormal degree of vascular leakage of red cells to lymph already by days 4–5 after irradiation, when the levels of blood platelets were still 100,000–400,000/μl blood. When the same high irradiation dose was given to animals with their hindlegs shielded, neither marked thrombocytopenia nor signs of abnormal vascular leakage developed. It appears, therefore, that newly produced platelets or some factor connected with platelet production must be available in order to prevent the abnormal microvascular leakage of red cells from developing.