Biodistribution of salicylates: a clue to the understanding of some effects and side effects.

According to our concept that biodistribution of salicylates (SA) might be an important factor of their mode of action the distribution of sodiumsalicylate (NaSA) and acetylsalicylic acid (ASA) was investigated in vivo and in vitro. It was shown that particular high concentrations of both compounds were found in vivo in the glandular stomach region and the kidney tubules of rats as well as in inflamed tissue. Quantitative studies showed that in chicken, in inflamed joints, higher concentrations as in plasma and about three times higher concentrations as in control joints were observed. In vitro studies using human erythrocytes suspended in buffer of different pH showed that added NaSA accumulated in these cells when the environmental pH was lowered from 7.4 to 6.8. From these results it is speculated that SA being weak acids accumulate within cells which are surrounded or bordering acidic fluids. This is the case in the stomach, the kidney and the inflamed tissue. This is where SA exert their effects and side effects.