ACETYLCHOLINE-INDUCED, CALCIUM-DEPENDENT NOREPINEPHRINE OUTFLOW FROM PERIPHERAL HUMAN-LYMPHOCYTES

Catecholamines (CA) were studied in peripheral human lymphocytes, as w ell as in the supernatants, after incubation with L-tyrosine and L-dih ydroxyphenylalanine (r-Dopa) for 1 h. The effect that the addition of acetylcholine (ACh), Veratridine, Ionomycin or KCl had on the outflow of norepinephrine (NE) from lymphocytes was also studied. The effect o f the addition of methoxyverapamil (D600, a Ca2+ channel blocker) and cholinergic antagonists had on the ACh-induced NE outflow was assessed . CA were determined by HPLC-ECD, both in the supernatant and in thee cell lysates. L-Tyrosine and L-Dopa significantly (P < 0.01) increased intracellular NE. Neither L-tyrosine, L-Dopa, nor vehicle induced a d etectable outflow of NE to the supernatants. ACh [120 mu M], Veratridi ne [100 mu M], Ionomycin [10 mu M] and KCl [50 mM] (with or without th e simultaneous addition of L-tyrosine or L-Dopa) all induced a detecta ble outflow of NE to the supernatant when added 5 min before the end o f incubation. NE was not detectable in the supernatant when the chemic als were added 10 to 20 min before the end of the incubation. When the chemicals were added at lower concentrations, erratic secretion or no secretion whatsoever was observed. D600 [100 mu M] was able to signif icantly (P < 0.01) reduce the ACh-induced NE outflow. Tetraethylammoni um (nicotinic antagonist), but not atropine (muscarinic antagonist), s ignificantly (P < 0.001) decreased the ACh-induced NE outflow. The out flow of NE from peripheral human lymphocytes was seen. NE secretion se ems to be ACh- and calcium-dependent since Veratridine, Ionomycin and KCl are able to induce Ca2+ entry by means of various mechanisms. The Ca2+ channel blocker employed in this study (D600) reduced the ACh-dep endent NE outflow. We can conclude that both ACh (through nicotinic re ceptors) and calcium are involved in the outflow of NE from peripheral human lymphocytes. (C) 1998 Elsevier Science B.V. All rights reserved .