Differential modification of opiate receptor activity by arylsulfatase treatment

Treatment with the enzyme arylsulfatase in vivo selectively attenuated the effect of analgesia induced by morphine, beta-endorphin or ethylketocyclazocine but not that induced by Sandoz FK33824 or D-ala2-D-leu5-enkephalin. The effect on morphine analgesia was indicated both by an increased morphine ED50 in the presence of a fixed dose of naloxone and by a decreased naloxone ED50 in the presence of a fixed dose of morphine. Arylsulfatase treatment in vivo also selectively affected in vitro ligand binding; Bmax values of the low affinity binding site of dihydromorphine, naloxone, D-ala2-D-leu5-enkephalin, D-ala2-met5-enkephalinamide and ethylketocyclazocine were decreased significantly while the Bmax values of the high affinity sites as well as the KD values of both the high and low affinity sites were affected little or not at all. The data suggest that the change induced by the enzyme may have been due to the alteration of certain constituents of the low affinity opiate binding site.