Previous studies reported that ACTH molecules influence chemotactic and phagocytic activities of hemocytes in the freshwater snail, Planorbarius corneus. The present study reveals that ACTH and CRF affect the release of biogenic amines. Hemocytes from P. corneus hemolymph incubated in vitro with ACTH for 15, 30, and 45 min released epinephrine, norepinephrine, and dopamine. The greatest release occurred after 15 min, while after 45 min the values were similar to those of the controls. Similar incubations with CRF also provoked a release of biogenic amines, this being mainly mediated by the release of endogenous ACTH. These data suggest that (i) ACTH and CRF provoke the release of biogenic amines; (ii) there is a direct relationship between CRF, ACTH, and biogenic amines, with the hemocytes as the target; (iii) exogenous ACTH can mimic an ancestral type of stress response; (iv) the major pathway of the stress response in P. corneus is mediated by a CRF-ACTH-biogenic amine axis. These data should help to unravel part of the complex molecular signaling mechanisms involved in the physiological/endocrinological reaction of invertebrate organisms to stress, and suggest that a stress response unexpectedly similar to that present in mammalian cells is detectable in invertebrates.
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