EFFECTS OF XANTHINE DERIVATIVES ON PHOSPHATIDYLCHOLINE SECRETION IN RAT TYPE-II PNEUMOCYTES IN THE PRESENCE OF ACTIVATED EOSINOPHILS

We have previously reported that activated eosinophils enhanced the ph osphatidylcholine (PC) secretion in type II pneumocytes. In this study , we have determined whether xanthine derivatives affect the PC secret ion increased by activated eosinophils. Theophylline enhanced the incr eased PC secretion at 10(-5) M. 8-Phenyltheophylline dose-dependently enhanced the PC secretion. The enhanced secretion by either theophylli ne at 10(-5) M or 8-phenyltheophylline was suppressed by superoxide di smutase in combination with catalase. Pentoxifylline did not enhance t he PC secretion increased by activated eosinophils, although it increa sed the PC secretion by itself. The PC secretion increased by theophyl line at 10(-3) M or pentoxifylline was not suppressed by superoxide di smutase in combination with catalase. The present results suggest that xanthine derivatives increased the PC secretion in the co-culture of type II pneumocytes and activated eosinophils possibly through the inh ibition of phosphodiesterases or the antagonism of adenosine receptors of the eosinophils.