Action of purine nucleosides on the release of intracellular enzymes from rat lymphocytes.

Rat lymphocytes incubated under hypoxic conditions in vitro show a time-dependent release of intracellular enzymes. As reported previously, enzyme release (lactate dehydrogenase) is decreased by metabolite, notably ATP and glucose, that contribute towards lymphocyte energy metabolism. The action of purine nucleosides in relation to enzyme release was investigated. Inosine was shown to decrease significantly lactate dehydrogenase release, whereas adenosine exerted a supportive action only at concentrations less than 0.5 mmol/l. Inosine decreased enzyme efflux maximally at concentrations of at least 2--3 mmol/l. The mechanism of inosine action was deduced to be primarily ribose 5-phosphate formation and its subsequent metabolism by energy-yielding pathways. Inosine was presumed also to enter the purine 'salvage pathway' and thereby maintain intracellular adenine nucleotide pools.