ADENOSINE ARRESTS APOPTOSIS IN LYMPHOCYTES BUT NOT IN PHAGOCYTES FROM PRIMARY LEUCOCYTE CULTURES OF THE TELEOST FISH, SPARUS AURATA L.

Adenosine and its derivatives have important biological functions, including the inhibition of immune responses and apoptosis induction. The aim of this work was to investigate whether adenosine and N6-cyclohexyladenosine regulate apoptosis in leukocyte cultures from the teleost, gilthead seabream (Sparus aurata L.) by flow cytometry using a double fluorescence staining method. Head kidney leukocytes (HKL´s) were cultured for 0, 24 or 48 h. The kinetics of FDA+/PI- (viable), FDA-/PI- (apoptotic) and FDA-/PI+ (necrotic) leukocyte subpopulations were followed during the culture process. Apoptosis was induced by addition of resveratrol or staurosporine to the culture media and the study was validated by transmission electron microscopy. Adenosine and N6-cyclohexyladenosine did not induce but decreased apoptosis of seabream HKL´s, in particular HK lymphocytes, after 24h in culture. Results raise the question whether apoptosis is differently modulated by purine nucleosides in fish lymphocytes and phagocytes and also in fish compared to mammalian cells.