EFFECT OF PLATELET-ACTIVATING-FACTOR ON THE PROCESS OF CELLULAR-DIFFERENTIATION OF HERPETOMONAS-MUSCARUM-MUSCARUM

The effects of platelet-activating factor (PAF), at doses ranging from 10(-6) M to 10(-10) M, on cell growth and on cell differentiation of Herpetomonas muscarum muscarum were investigated. Cell differentiation was evaluated by both light and electron microscopy. At the concentra tions used, PAF did not interfere with the protozoan growth. However, parasites grown in the presence of PAF (10(-6) M) were significantly m ore differentiated than those grown in the absence of PAF, since the f irst day of culture. On the first two days of culture, PAF doses rangi ng from 10(-10) M to 10(-7) M, did not significantly interfere with th e differentiation of these parasites, although after the third day of culture, all PAF doses used significantly increased the protozoan diff erentiation. Specific PAF receptor antagonists totally abrogated (WEB 2086 and WEB 2170) or significantly decreased (BN 52021) PAF effect on cell differentiation. These findings indicate PAF triggers the proces s of cell differentiation in Herpetomonas muscarum muscarum and sugges t these parasites have receptors for PAF.