[Studies on the synthesis and structure-activity relation of deltorphin I analogues]

Endogenous opioid deltorphin I (DEL I) and its three analogues (progressive, stepwise repositioning of Asp from 5 to 7) were synthesized by solid phase method. DEL I at 10(-14)-10(-10) mol.L-1 in vitro and at 0.5-5 micrograms.kg-1 in vivo was found to increase the percentages of erythrocyte rosette forming cells (E-RFC) and red blood cell C3b receptor garland (RBC-CR1). This augmentative effect of DEL I was antagonized by naloxone. The results indicate that DEL I enhanced the immune function of rats. The order (from strong to weak) of the analgesic and immune activity was shown to be Asp4, Asp7, Asp5, Asp6 and Asp4, Asp7, Asp6, Asp5 respectively.