Critical mass of splenic autotransplant needed for the development of phagocytic activity in rats

When total splenectomy is inevitable, heterotopic splenic autotransplantation seems to be the only alternative to maintain the functions of the spleen. The present study was carried out to analyse the critical mass of splenic autotransplant (SAT) for the development of phagocytic activity in rats. Wistar rats were submitted to total splenectomy (TS) alone or in combination with slices of SAT ranging from an average rate of 21·9% (one slice) to 100% (five slices) of the total splenic mass implanted into the greater omentum. Sixteen weeks after the beginning of the experiment, the animals were inoculated intravenously with a suspension of Escherichia coli labelled with Tc-99m. After 20 min, the rats were killed and the liver, lung and spleen or SAT, as well as blood samples were removed to determine the percentage of labelled bacteria uptake in these tissues. As the percentage of the total splenic mass contained in the SAT increased, the bacteria remaining in the blood decreased. From the implant of 26% up to the implant of the total splenic mass (100%) there was no difference in the bacteria remaining in the blood between the healthy animals of the control group and those submitted to TS combined with SAT. This finding shows that the critical mass needed for the development of phagocytic activity of macrophages in splenic autotransplants in adult rats is 26% of the total splenic mass.