title: Inhibition and facilitation by pimobendan, a calcium sensitizer, of catecholamine secretion from bovine adrenal chromaffin cells.
abstract: The effects of pimobendan, a Ca(2+) sensitizer with inhibitory action against cyclic-GMP-inhibited phosphodiesterase (PDE-III), on catecholamine (CA) secretion were studied in bovine adrenal chromaffin cells. In intact cells, pimobendan (10 - 100 microM) inhibited CA secretion stimulated by acetylcholine (10 and 30 microM) and 1,1-dimethyl-4-phenyl-piperazinium (DMPP) (3 and 10 microM), but facilitated CA secretion stimulated by high K(+) (30 mM), histamine (3 microM), and angiotensin-II (3 microM). Histamine and angiotensin-II had no effect on CA secretion in Ca(2+)-free medium. The inhibition or facilitation by pimobendan of the stimulation-evoked CA secretion was not affected by H-89 (1 microM) and H-8 (30 microM), inhibitors of cyclic-AMP-dependent protein kinase. Milrinone (10 and 30 microM) and amrinone (100 and 300 microM), inhibitors of PDE-III, did not affect the stimulation-evoked CA secretion. In beta-escin-permeabilized cells, pimobendan (10 - 100 microM) did not affect CA secretion stimulated by Ca(2+) (0.1 - 10 microM) in the presence and absence of MgATP (2 mM). These results indicate that pimobendan has dual effects, inhibition and facilitation, on CA secretion. The inhibition may be due to an inhibitory action on nicotinic receptors and the facilitation may be due to a facilitatory action on stimulation-induced Ca(2+) influx. Neither Ca(2+) sensitizing nor PDE-III inhibiting actions seem to be related to these effects.
authors.affiliation: Department of Pharmacology, The Nippon Dental University School of Dentistry at Niigata, Japan. kuwajima@ngt.ndu.ac.jp
authors.forename: Haruhiro
authors.initials: H
authors.lastname: Kuwashima
authors.forename: Chiaki
authors.initials: C
authors.lastname: Matsumura
authors.forename: Tomohiko
authors.initials: T
authors.lastname: Kimura
mesh_terms: D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000037:antagonists & inhibitors*; D000109:Acetylcholine / Q000494:pharmacology; D000311:Adrenal Glands / Q000166:cytology*; D000676:Amrinone / Q000494:pharmacology; D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002395:Catecholamines / Q000378:metabolism*; D002417:Cattle; D002478:Cells, Cultured; D019439:Chromaffin Cells / Q000187:drug effects* / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D054684:Cyclic Nucleotide Phosphodiesterases, Type 3; D004246:Dimethylphenylpiperazinium Iodide / Q000494:pharmacology; D006632:Histamine / Q000494:pharmacology; D007546:Isoquinolines / Q000494:pharmacology; D020105:Milrinone / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D011724:Pyridazines / Q000494:pharmacology*; D013449:Sulfonamides
chemical_list: D002395:Catecholamines; D007546:Isoquinolines; D011724:Pyridazines; D013449:Sulfonamides; D000804:Angiotensin II; C041648:pimobendan; D004246:Dimethylphenylpiperazinium Iodide; D006632:Histamine; D017868:Cyclic AMP-Dependent Protein Kinases; D015105:3',5'-Cyclic-AMP Phosphodiesterases; D054684:Cyclic Nucleotide Phosphodiesterases, Type 3; D020105:Milrinone; D000676:Amrinone; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide; D000109:Acetylcholine; D011188:Potassium; D002118:Calcium