Inhibition by clinically used dyes of prostaglandin inactivation in rat and human lung.

1. The effect of several clinically used dyes on prostaglandin E2 (PGE2) inactivation was studied in rat and human isolated lung. 2. All the dyes, given as infusions through the pulmonary circulation, inhibited the inactivation of PGE2 as measured by bioassay. The action of the dyes was readily reversible on stopping the infusion. 3. The concentration producing 30% inhibition varied from 0.6 microM for indocyanine green to over 100 micro M for methylene blue. 4. Inhibition of PGE2 inactivation was also observed when the dyes were given as bolus injections during PGE2 infusions through the lung. 5. These dyes are therefore not physiologically inert as they had previously been thought to be and their interaction with prostaglandins may affect the variables they are used to measure.