SELECTIVE SYNTHESIS OF A SECRETORY PHOSPHOLIPASE A(2) DURING ADHERENCE OF GUINEA-PIG ALVEOLAR MACROPHAGES

We have previously shown that freshly collected guinea-pig alveolar ma crophages (AM) showed low levels of sPLA(2) activity. This activity in creased progressively in cultured AM, to reach levels 40-50-fold above basal values within 20 h of adhesion. This increase was abrogated in the presence of actinomycin D or cycloheximide and in experimental con ditions that prevent the adherence of AM, suggesting that AM produce a n sPLA, through RNA and protein synthesis-dependent processes induced by their adherence. Adherence of AM induced selectively the synthesis of sPLA, since the level of the cPLA(2) activity did not change signif icantly with the duration of adhesion. In contrast to the cPLA(2) acti vity, which was mainly recovered in the soluble fraction of AM sonicat es, the sPLA, activity was located in the membrane fractions. The incr ease observed in the sPLA, activity occurred independently from the re lease of AA by stimulated AM, suggesting that these two processes are distinct.