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CARDIAC β‐ADRENOCEPTOR CHANGES IN EXPERIMENTAL HYPERTHYROIDISM IN DOGS
Author(s) -
Hoey Andrew,
Brown Lindsay,
Marchant Catherine,
Atwell Rick,
Sernia Conrad
Publication year - 1992
Publication title -
clinical and experimental pharmacology and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 103
eISSN - 1440-1681
pISSN - 0305-1870
DOI - 10.1111/j.1440-1681.1992.tb00413.x
Subject(s) - chronotropic , medicine , isoprenaline , endocrinology , iodocyanopindolol , triiodothyronine , in vivo , saline , cyclase , adenylate kinase , basal (medicine) , antagonist , chemistry , stimulation , heart rate , receptor , biology , thyroid , intrinsic activity , agonist , blood pressure , microbiology and biotechnology , insulin
SUMMARY 1. Triiodothyronine (T 3 ; 1.0 mg/kg per day subcutaneously) was administered to 10 dogs for 14 days; 10 saline‐treated dogs served as controls. T 3 ‐treated dogs showed the expected physiological responses of hyperthyroidism; further, chronotropic responses to isoprenaline in vivo were significantly increased in T3‐treated dogs. 2. β‐Adrenoceptor subtype density was measured in membrane preparations by displacement of l25 I‐iodocyanopindolol binding by the selective β 2 ‐adrenoceptor antagonist, ICI 118, 551. T 3 treatment led to a 93% increase in right atrial β 1 ‐adrenoceptor density and a 141% increase in left ventricular β 1 ‐adrenoceptor density; β 2 ‐adrenoceptor densities in right atrial, left ventricular and lung membranes were unchanged. 3. T 3 ‐treatment did not change basal or maximally stimulated adenylate cyclase activities in left ventricular membranes. 4. Thus, the cardiovascular changes in experimental hyperthyroidism in dogs were accompanied by an increased chronotropic response in vivo to isoprenaline and an increased β 1 ‐adrenoceptor density in atrial and ventricular membranes. However, there was no corresponding change in basal or maximal responsiveness of adenylate cyclase in ventricular membranes.