Hepatectomy in the Salamander with Special Reference to Hemopoiesis and Cytology of the Liver Remnant.

Abstract

In the salamander, Triturus viridescens, granulocytopoiesis is normally restricted almost completely to the subcapsular region of the liver, erythrocytopoiesis and thrombocytopoiesis to the spleen. A relatively very slight granulocytopoietic activity occurs in the intestinal mucosa. As previously reported, splenectomy does not effect a compensatory erythrocytopoietic or thrombocytopoietic activity in the lympho-granulocytopoietic envelope of the liver. Following splenectomy the processes of erythrocyte and thrombocyte production are shifted to the general circulation. 1 The reverse experiment also gives a negative result; hepatectomy effects no compensatory granulocytopoietic activity in the spleen. Since the same ancestral cell, the lymphoid hemoblast, occurs in both regions, as a mesenchymal derivative, it must be concluded that certain specific conditions in spleen and liver are restrictive as regards hemocytopoietic stimuli. The differential stimuli for erythrocyte and granulocyte formation presumably inhere in some element in the character of the blood supply; the perihepatic granulocytopoietic region contains a very meager vascularization as compared with the abundant sinusoidal venous system of the spleen.

Total hepatectomy results in death within 9 days (20 specimens). The survival time is uninfluenced by coincident splenectomy. Removal of half of the liver (left and middle lobes) produces no noticeable hemopoietic effects (30 specimens). Such experimental animals lived until killed during the third month for study of the remaining liver tissue. These one-lobe livers show no microscopic evidence of regeneration. The remaining lobe, however, is somewhat enlarged by the twenty-seventh day, and has apparently effected satisfactory histologic and physiologic restoration (Fig. 1). The effect of semi-hepatectomy appears to be one of compensatory hypertrophy. Since no proliferative activity was observed at the several progressive stages studied the exact method of this hypertrophy remains uncertain. The enlargement is due in part to a thickening of the granulocytopoietic capsule, where very active mitosis occurs apparently in compensation for the loss of the excised portion.