title: Effects of elastase on contractility and morphology of elastic tissue in isolated guinea pig papillary muscles.
abstract: Elastase (ELA) is an enzyme catalyzing the digestion of elastin, an essential constituent of elastic fibers. Using isolated guinea pig papillary muscles, we examined the effect of ELA (3 x 10(-7) -3 x 10(-4) g/ml) on resting tension (RT) and twitch tension (TT). The effects of ELA on elastic fibers located in the subendocardium were examined histologically. A relatively high concentration of ELA (3 x 10(-4) g/ml) increased TT transiently, with progressive decreases in RT. In contrast, a relatively low concentration (3 x 10(-5) g/ml) decreased both TT and RT straightforwardly. Much lower concentrations (3 x 10(-6) -3 x 10(-7) g/ml) did not reveal significant effects. The ELA-induced increases in TT were unaffected in the presence of atenolol (10(-5) g/ml), ouabain (10(-7) M) or ryanodine (10(-6)M). ELA did not increase the maximum rate of rise of slow action potentials recorded using standard microelectrodes. ELA (3 x 10(-5) g/ml) decreased the maximum TT obtained at optimal RT or Lmax, and decreased the slope of the ascending and descending limbs of the TT-RT relation curve (Frank-Starling's). Electron-microscopic findings revealed that subendocardial elastin was mostly digested at ELA concentrations of 3 x 10(-5) -3 x 10(-4) g/ml. These findings suggest that the decrease of RT by ELA may be, at least in part, caused by a decomposition of the elastic fibers. On the other hand, the increase of TT by ELA could not be attributed to a release of endogenous catecholamine, an inhibition of Na+, K(+)-pump, a release of Ca2+ from sarcoplasmic reticulum, or an increase of slow inward current.
authors.affiliation: Department of Physiology, Oita Medical University, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Sato
authors.forename: S
authors.initials: S
authors.lastname: Imanishi
authors.forename: M
authors.initials: M
authors.lastname: Arita
authors.forename: T
authors.initials: T
authors.lastname: Shimada
mesh_terms: D000818:Animals; D004305:Dose-Response Relationship, Drug; D004547:Elastic Tissue / Q000187:drug effects* / Q000473:pathology; D004549:Elastin / Q000378:metabolism; D004562:Electrocardiography / Q000187:drug effects*; D004699:Endocardium / Q000187:drug effects / Q000473:pathology; D005260:Female; D006168:Guinea Pigs; D006339:Heart Rate / Q000187:drug effects; D008297:Male; D008854:Microscopy, Electron; D009200:Myocardial Contraction / Q000187:drug effects*; D010196:Pancreatic Elastase / Q000494:pharmacology*; D010210:Papillary Muscles / Q000187:drug effects* / Q000473:pathology
chemical_list: D004549:Elastin; D010196:Pancreatic Elastase