title: Physiological effects and biochemical properties of a serum protein that produces positive inotropic and chronotropic effects on isolated guinea pig atria.
abstract: Isolated left and right guinea pig atria were used as a bioassay for the detection of an endogenous cardioactive substance in bovine serum. Serum, buffer exchanged to Krebs-Henseleit solution, produced positive inotropic and chronotropic effects on the isolated guinea pig atria. The cardiotonic effects were unaffected by the combined presence of propranolol and methysergide (both 10(-6)M) and were also dissimilar in time course from other known cardiotons such as catecholamines and cardiac glycosides. Following ultrafiltration (using XM100A Amicon membranes), activity was found solely in the retentate fractions and was therefore probably due to a large molecular weight (> 100 kDa) substance or a small molecule bound to a large protein. The cardioactive factor (CF) in the whole serum was heat labile, sensitive to acidification, exposure to potassium bromide and equilibration to physiological buffers of a low ionic strength. Isolation by conventional protein purification techniques was unsuccessful due to the labile nature of the active molecule(s) when exposed to non-physiological experimental conditions. Physical and biochemical properties of the CF which may help avoid inactivation are discussed for future experiments aimed at elucidating the nature and identity of the cardiotonic principle.
authors.affiliation: Department of Medicine, University Clinical Departments, Daulby Street, Liverpool, L69 3GA UK. m.hussain@liverpool.ac.uk
authors.forename: Munir
authors.initials: M
authors.lastname: Hussain
authors.forename: Alzbeta
authors.initials: A
authors.lastname: Chorvatova
authors.forename: Jaipaul
authors.initials: J
authors.lastname: Singh
mesh_terms: D000818:Animals; D001798:Blood Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000494:pharmacology*; D001965:Bromides / Q000494:pharmacology; D002316:Cardiotonic Agents / Q000737:chemistry* / Q000302:isolation & purification / Q000494:pharmacology*; D006168:Guinea Pigs; D006321:Heart / Q000187:drug effects* / Q000502:physiology; D006325:Heart Atria / Q000187:drug effects; D066298:In Vitro Techniques; D009200:Myocardial Contraction / Q000187:drug effects*; D017680:Potassium Compounds / Q000494:pharmacology; D013696:Temperature
chemical_list: D001798:Blood Proteins; D001965:Bromides; D002316:Cardiotonic Agents; D017680:Potassium Compounds; C039004:potassium bromide