title: Positive inotropic effect of thyrotropin-releasing hormone on isolated rat hearts.
abstract: The effects of thyrotropin releasing hormone (TRH) on the contractility of electrically stimulated and perfused isolated rat hearts were investigated. TRH in the range of 0.1-10 mumol/l was found to exert a positive inotropic effect on cardiac contractility, which however qualitatively differed at lower vs. higher concentrations of the hormone: at 1 mumol/l, TRH was found to significantly enhance the rate of contraction as well as that of relaxation (by 23.2 +/- 3.7 and 27.8 +/- 7.7%, respectively), which culminated in an increased peak contractile force. However, at 10 mumol/l, the positive inotropic effect of TRH (i.e. the increase in peak contractile force) was smaller than at 1 mumol/l, which apparently was due to both a reduced TRH-induced elevation in the rate of contraction (12.4 +/- 3.2%) and a TRH-induced decrease in relaxation rate (11.1 +/- 8.1%). Since TRH is expressed in the heart, the above findings suggest that, in addition to its CNS-mediated cardiovascular effects, TRH modulates cardiac contractility as an autocrine regulator in a concentration-dependent manner, which likely involves more than one TRH receptor and associated signaling pathway.
authors.affiliation: Medical College of Georgia, Department of Physiology and Endocrinology, Augusta 30912, USA.
authors.forename: R
authors.initials: R
authors.lastname: Socci
authors.forename: R C
authors.initials: RC
authors.lastname: Kolbeck
authors.forename: L G
authors.initials: LG
authors.lastname: Mészáros
mesh_terms: D000818:Animals; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D006321:Heart / Q000187:drug effects / Q000502:physiology; D066298:In Vitro Techniques; D009200:Myocardial Contraction / Q000187:drug effects*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology*; D013997:Time Factors
chemical_list: D013973:Thyrotropin-Releasing Hormone