Hemostasis following inoculation and during spreading of colon carcinoma in the rat.

Platelet function following inoculation of chemically induced carcinoma was evaluated in the rat. The original line of tumor (NGW1) was obtained using N-methyl-N-nitrosoguanidine. After trypsin homogenation a cell suspension of 0.3 X 10(6) viable tumor cells was injected subserosally in the cecum of each animal. Controls received injections of equal volumes of 0.9% NaCl solution or trypsin. The animals were subjected to laparotomy 2, 4, and 6 weeks after inoculation. Platelet function was assessed in vivo by measuring bleeding time and blood loss during mesenteric vessel transection or liver resection upon laparotomy. Hemoglobin, hematocrit, platelet count, activated partial thromboplastin time, platelet aggregation, thromboxane B2, platelet factor 4, and fibrinogen levels were evaluated after sacrifice by exsanguination. Significant decrease in bleeding time and blood loss was observed in animals with local primary tumors as well as in rats with lymph node metastases. Hemoglobin and hematocrit were decreased in the presence of metastases. Platelet count was not changed. Activated partial thromboplastin time was not affected by the presence of tumor. Platelet aggregation in vitro was accelerated in the presence of primary tumor or lymph node metastases, as well as following addition of tumor cells to platelet suspensions. No changes in thromboxane B2 or platelet factor 4 could be registered. Fibrinogen levels were decreased in the presence of liver metastases. Enhancement of primary hemostasis and platelet function in the presence of colon carcinoma in the rat was demonstrated both in vivo and in vitro. Direct or indirect interaction of the tumor cell with thrombocytes may play a role in determining the metastatic potential of the neoplasm.