Dynorphin in bovine adrenal medulla. I. Detection in glandular and cellular extracts and secretion from isolated chromaffin cells.

The presence and secretion of immunoreactive dynorphin in bovine adrenal medulla and isolated adrenal chromaffin cells were examined and compared with those of immunoreactive leucine-enkephalin. Using an antiserum raised against dynorphin-(1-13), a sensitive and highly specific radioimmunoassay was developed. A nearly intact antigen was required for recognition by the antiserum since it did not react with leucine-enkephalin and reacted poorly with dynorphin-(1-12) (cross-reactivity 0.5%) and other fragments of dynorphin-(1-13). On the other hand, the antibody used for detection of leucine-enkephalin did not cross-react with dynorphin(1-13). Adrenal medulla acid extracts contained 195 times more immunoreactive leucine-enkephalin than dynorphin. However, the concentration of immunoreactive dynorphin in acid extract of freshly isolated adrenal chromaffin cells was only 1.4 times smaller than that of leucine-enkephalin. Incubation of the isolated chromaffin cells in the presence of acetylcholine, nicotine, high potassium, but not muscarine, induced a concomitant release of immunoreactive dynorphin (3.5-9% of total cell content) and leucine-enkephalin (6.5-11.4% of total cell content).