The binding of a specific muscarinic antagonist to subcellular fractions of the bovine caudate nucleus.

adjuvant; a second intramuscular injection of an equal amount of antigen in Freund’s incomplete adjuvant was given 1 month later. Then 1 week later rabbits were bled, and a crude immunoglobulin preparation was made by the method of Kekwick (1940). The results shown in Fig. 1 suggest that the human neuroblastoma line contains monoamine oxidase activity of an A type, whereas that of MC63 cells is predominantly type B. At a concentration of 10m-clorgyline, monoamine oxidase from IMR32 cells was almost completely inhibited, whereas that from MC63 cells was only slightly so. To clarify further the possible differences between monoamine oxidase in the two cell lines, 0.5 % (w/v) Triton X-100 extracts of the two cell lines were made to react with antiserum raised against purified human placental monoamine oxidase. The purification of this placental enzyme is briefly described in Scheme 1. This antiserum reacted with crude human placental mitochondrial extracts in 0.5 % (w/v) Triton X-100 to form a single precipitin line in double-diffusion tests, but failed to react with 0.5 % (w/v) Triton X-100 extracts of human platelets, or partially purified human platelet monoamine oxidase. These preparations should contain only type B enzyme (see Donnelly et al., 1976). The antiserum also reacted with crude extracts of IMR32-cell mitochondria but not those prepared from MC63 cells, even when the latter extract was in fourfold excess with respect to monoamine oxidase activity. Further work is required to clarify the nature of the antigen recognized by this antiserum. However, it is apparent that the neuroblastoma line expresses a form of monoamine oxidase with properties similar to those described for type A enzyme and can be distinguished from the form expressed in the HeLa-cellline derivative MC63.