GABA content and GAD activity in colon tumors taken from patients with colon cancer or from xenografted human colon cancer cells growing as s.c. tumors in athymic nu/nu mice.

A significantly high GABA level and GAD activity was found in human colon cancer tissue as compared with normal macroscopically unchanged human colon wall taken from the same patients. Similarly in athymic nu/nu mice transplanted with human colon adenocarcinoma cells established in in vitro culture (line CX-2) the high level of GABA accompanied by high GAD activity was found in subcutaneously growing tumors as compared with the unchanged colon wall and unchanged skin tissue from the same tumor bearing mice. Interestingly, the level of GAD activity in the macroscopically unchanged colon tissue of mice transplanted with tumor cells were increased in comparison with normal colon of healthy control mice. For the skin, only GAD activity was higher in the material coming from tumor bearing mice than in the material from normal control mice, whereas GABA level was even lower in the skin of tumor inoculated mice compared with control group. An increase in GABA level and in GAD activity can perhaps reflect a local immune response to the neoplastic process. The observed direction of GABA metabolism in tumor of the colon indicates a possibility to interfere in this process using the agonists of the GABA-ergic system.

Influence of antiplatelet drugs on occlusion of arteriovenous fistula in uraemic patients.

A long-standing arteriovenous (A-V) fistula may develop thrombotic complications. In 20 patients on intermittent peritoneal dialysis (IPD) arteriovenous fistula was made surgically. We evaluated the efficacy of three antiplatelet drugs: Ibustrin (Group A), sulphinpyrazone (Group B) and alpha-tocopherol (Group C) in preventing thrombotic occlusion of A-V fistulas. Results of the trial indicate that the three drugs significantly reduce spontaneous platelet aggregation and ADP induced aggregation. The heparin neutralizing activity was significantly increased during treatment. Significant prolongation of bleeding time was observed only in Groups B and C. In patients receiving antiplatelet drugs no occlusion of A-V fistulas was observed. In the control group such complications occurred in 3 of the 20 patients. Our results indicate that antiplatelet drugs by inhibiting the platelet function may prevent thrombotic occlusions of A-V fistulas in IPD patients.