Production of thromboxanes by transformed lymphocytes--effect on heart contractility

We studied the effect of transformed lymphocytes from patients with chronic lymphocytic leukaemia (CLL) and the Raji cell (Raji) on the response of rat isolated atria to sodium arachidonate (AA). In contrast to normal lymphocytes, CLL cells and Raji cells decrease the contractile tension of rat isolated atria. Addition of exogenous AA (1.98 X 10(-6) M) to Raji, further reduced the isometric developed tension. Time of culture of Raji was important, as the negative inotropic effect was greater at 72 h than at 24 h of culture. Living cells were required and cell-free supernatants were inactive. Preincubation of CLL cells or Raji with cyclooxygenase inhibitors (acetyl salycilic acid, indomethacin) or inhibitors of thromboxane (TX) synthesis (imidazole, L-8027) abolished the negative inotropic response suggesting the contribution of TXs. L-8027 also reduced the growth rate of Raji cells, indicating that TXs may play a role in the regulation of cell division. The production of TXs by CLL and Raji cells from both endogenous and exogenous sources provided additional support to this hypothesis and suggested that activation of this metabolic pathway may be related to cell transformation.