title: Characterization of cardiac beta-adrenergic receptors in the guinea pig heart: application to study of beta-adrenergic receptors in shock models.
abstract: The myocardial response to catecholamines is significantly diminished in many types of shock or heart failure. The guinea pig heart is an ideal model for the study of shock, as it is relatively inexpensive, and the cardiovascular system of the guinea pig most closely resembles that of the human. Using this model, we have developed techniques to characterize and quantitate changes in beta-adrenergic receptors (beta AR) in the guinea pig heart after burn injury. Preliminary experiments were performed to determine the optimum binding conditions, e.g., incubation time and conditions, protein concentrations, rinsing, etc. Additional experiments were conducted using agonists and antagonists to characterize the rank order of potency and stereospecificity of the beta AR. Crude membrane preparations (50 micrograms/250 microliters) from sham-burned and burned hearts were incubated with 8-10 concentrations of 125I-cyanopindolol (10-450 pM) at 37 degrees C for 1 hr. Under these conditions, binding assays were linear with respect to protein concentration and time. Alprenolol (10 microM) was used to determine nonspecific binding. The membrane preparations used in this study bound both agonists and antagonists with a rank order of potency and stereospecificity characteristic of a beta-adrenergic receptor. Finally, agonist competition curves were performed with isoproterenol in the presence and absence of Gpp(NH)p to determine receptor regulation by the Gs protein. Analysis using computer-assisted techniques suggests that the fraction of high-affinity beta-receptors is significantly reduced after burn injury (41.2 +/- 4.7%) compared to sham-burned controls (54 +/- 2%, P < or = 0.023).(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Surgery, University of Texas Southwestern Medical Center, Dallas 75235-9031.
authors.forename: T M
authors.initials: TM
authors.lastname: Kaufman
authors.forename: J W
authors.initials: JW
authors.lastname: Horton
mesh_terms: D000526:Alprenolol / Q000378:metabolism; D000818:Animals; D001667:Binding, Competitive; D002056:Burns / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D005374:Filtration / Q000295:instrumentation; D006165:Guanylyl Imidodiphosphate / Q000378:metabolism; D006168:Guinea Pigs; D007457:Iodine Radioisotopes; D020120:Iodocyanopindolol; D007545:Isoproterenol / Q000378:metabolism; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D010869:Pindolol / Q000031:analogs & derivatives / Q000378:metabolism; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*; D012769:Shock / Q000503:physiopathology*
chemical_list: D007457:Iodine Radioisotopes; D011943:Receptors, Adrenergic, beta; D006165:Guanylyl Imidodiphosphate; D020120:Iodocyanopindolol; D000526:Alprenolol; D010869:Pindolol; D007545:Isoproterenol