Effect of pentazocine on the cytotoxicity of cortisone-resistant lymphocytes from mouse thymus

Pentazocine and its related compounds were examined for their effect on the cytotoxicity of cortisone-resistant lymphocytes (CR lymphocytes) against Ehrlich carcinoma cells. The following compounds were used: pentazocine, naloxone, levallorphan, eptazocine and morphine. CR lymphocytes were obtained from the thymus or spleens of mice injected i.p. with hydrocortisone acetate (125 mg/kg) 2 days before harvesting the lymphocytes. The mixture of tumor cells and CR lymphocytes was inoculated s.c. into mice after incubation in the presence or absence of 10 microM drugs. Five weeks after inoculation, the percentage of mice developing a solid tumor among the recipients given the pentazocine-treated cell mixture of tumor cells and thymic CR lymphocytes was significantly smaller than the percentage in recipients given the cell mixture treated with or without other drugs (percent tumor takes: 21% and about 80%, respectively). Splenic CR lymphocytes did not show any cytotoxic effect, irrespective of the drug treatment. The pretreatment of CR lymphocytes or Ehrlich cells with 10 microM pentazocine did not affect the cytotoxicity of thymic and splenic CR lymphocytes. The proportion of the lymphocyte-conjugated tumor cells was significantly increased when the mixture of CR lymphocytes and tumor cells was incubated in the presence of pentazocine. The present results indicate that the cytotoxicity of thymic CR lymphocytes is enhanced by pentazocine possibly through the increase in the proportion of the lymphocyte-conjugated tumor cells but enhanced not by the other drugs.