[3H]-Dynorphin A (1-8): degradation profile and binding characteristics in brain homogenates

[3H]-Dynorphin A (1-8) was degraded in brain homogenates at 25 degrees and even at 0 degree C. The peptidase inhibitors bestatin and captopril almost completely protected[3H]-dynorphin A (1-8) from degradation at 0 degree C but had only little effect on binding at this temperature. At 25 degrees C, the binding of [3H]-dynorphin A (1-8) was markedly improved by addition of bestatin, captopril and L-leucyl-L-arginine, which afforded some, but not complete protection from degradation. The results of saturation binding assays at 25 degrees C in the presence of the peptidase inhibitors were variable. However, it was found from saturation binding assays at 0 degree C that the maximum binding capacity for [3H]-dynorphin A (1-8) at the kappa-site is similar to that of [3H]-(-)-bremazocine and [3H]-dynorphin A (1-9).