Effects of adenosine on guinea pig pulmonary eosinophils

Extracellular adenosine has pharmacological activity on a wide variety of cell types and may play an important role as an inflammatory modulator with both pro- and anti-inflammatory activities. These studies examine the effects of adenosine on guinea pig pulmonary eosinophils. Adenosine alone did not directly induce superoxide (O-2(-)) production. Pretreatment with adenosine primed the O-2(-) response of guinea pig pulmonary eosinophils following the addition of 1 or 10 mu M platelet-activating factor (PAF). Priming was seen at adenosine concentrations greater than 1 mu M and was maximal at 100 mu M. At this maximal dose, adenosine priming increased the O-2(-) response to 1 mu M and 10 mu M PAF by 86% and 51%, respectively. Priming by adenosine was not seen when ionomycin or phorbol myristate acid (PMA) were used as agonists, In fura-2 loaded eosinophils, the addition of 100 mu M adenosine resulted in a small but significant rise in intracellular calcium of 54.4 +/- 9.2 nM above baseline. In contrast, similar adenosine concentrations had no effect on cytosolic calcium levels in guinea pig neutrophils. These data demonstrate a pro-inflammatory role for adenosine in elicited guinea pig pulmonary eosinophils.