We have shown recently, that inhibition of renal renin secretion (RS) by a high renal perfusion pressure (RPP) requires A1 adenosine receptors. In order to characterize the source of adenosine in this process we now investigated the pressure dependent regulation of RS in isolated perfused kidneys of mice with targeted deletion of ecto-5'-nucleotidase (e-5'NT), the enzyme responsible for extracellular adenosine formation from AMP. RS from kidneys of e-5'NT-/- and e-5'NT+/+ were not different at control RPP of 90mmHg. Reduction of RPP from 90 to 50mmHg stimulated RS 2.9-fold in e-5'NT-/- and 2.5-fold in e-5'NT+/+. Increasing RPP from 90 to 130 mmHg inhibited RS to 65% in kidneys of e-5'-NT+/+ (p<0.05), while it did not suppress RS in kidneys of e-5'NT-/- (110% of control). In contrast, RS was inhibited to the same extent in both genotypes by the A1 adenosine receptor agonist CHA. We next considered the macula densa, shown to release ATP in dependence on the tubular salt concentration, as the source of adenosine precursors. However, blockade of macula densa salt transport by bumetanide did not attenuate the inhibition of RS by an elevation of RPP from 90 to 130mmHg (55% of control), arguing against this hypothesis. In conclusion our data demonstrate that adenosine, generated by extracellular nucleotide hydrolysis, is critical for the pressure dependent inhibition of renin release while it appears without effect for the stimulation by a reduction of perfusion pressure.