title: Unexpected contractile response from the G-protein activator mastoparan in cardiac myocytes.
abstract: Mastoparan preferentially activates the G protein Gi in transmembrane signalling pathways. In heart tissue Gi couples receptors to negative inotropy so we have examined the effect of mastoparan on contractility in cardiac myocytes electrically stimulated at 0.5 Hz. Mastoparan (10(-5) mol/l) caused a time-dependent increase in cell shortening to a maximum of 83.7 +/- 18.0% (n = 7) of the resting cell length at between 4 and 7 min. This could be the result of either stimulation of other G proteins or the release of beta gamma subunits from Gi which activate phospholipase C.
authors.affiliation: Department of Biochemistry, Dr Karl Thomae GmbH, Biberach an der Riss, Germany.
authors.forename: J C
authors.initials: JC
authors.lastname: Van Meel
authors.forename: R M
authors.initials: RM
authors.lastname: Haigh
mesh_terms: D000818:Animals; D004558:Electric Stimulation; D004789:Enzyme Activation; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006168:Guinea Pigs; D066298:In Vitro Techniques; D036341:Intercellular Signaling Peptides and Proteins; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects*; D009206:Myocardium / Q000166:cytology; D010455:Peptides; D015398:Signal Transduction / Q000187:drug effects; D010738:Type C Phospholipases / Q000378:metabolism; D014862:Wasp Venoms / Q000494:pharmacology*
chemical_list: D036341:Intercellular Signaling Peptides and Proteins; D010455:Peptides; D014862:Wasp Venoms; C037500:mastoparan; D010738:Type C Phospholipases; D019204:GTP-Binding Proteins