Rats fed a purified diet low in pantothenic acid developed granulocytopenia and anemia singly or in combination. In the former, the marrow showed marked depletion of granulocytes, particularly of the more mature cells, and a slight increase in erythroid cells. In combined granulocytopenia and anemia the granulocytes of the marrow were still further reduced and the erythroid cells were also depleted. Marked reduction in the number of megakaryocytes occurred both in the granulocytopenic and in the granulocytopenic and anemic rats. Purpura was noted grossly in about 25 per cent of the rats of both groups. In anemia without accompanying granulocytopenia the marrow granulocytes showed slight to moderate depletion, whereas the erythroid index (mean) was not significantly lowered. Megakaryocytes were moderately reduced.
Lymphoid tissue—spleen, thymus, and cervical nodes—showed atrophy of variable degree, most marked in the thymus.
Adrenal glands showed marked depletion of cortical lipoids and rarely hemorrhage and necrosis.
Following treatment with combined folic acid, pantothenic acid, and niacinamide, granulocytopenic rats responded by showing a prompt rise in lymphocyte and polymorphonuclear leukocyte count, marked granulocyte response of the bone marrow, increased splenic hematopoiesis, lymphoid hyperplasia, and increased lipoid content of the adrenal glands.