Inhibitory effects of calcium channel blockers on thyroid hormone uptake in neonatal rat cardiomyocytes

• Published in: American journal of physiology. Heart and circulatory physiology 2001-11, Vol.281 (5), p.H1985-H1991
• Main Authors: Verhoeven, Frank A, Moerings, Ellis P. C. M, Lamers, Jos M. J, Hennemann, Georg, Visser, Theo J, Everts, Maria E
• Format: Article
• Language: English
• Subjects: Adenosine Triphosphate - metabolism; Animals; Animals, Newborn; Biological Transport - drug effects; Calcium - pharmacology; Calcium Channel Blockers - pharmacology; Cell Membrane - metabolism; Cells, Cultured; Diltiazem - pharmacology; Iodine Radioisotopes; Muscle Fibers, Skeletal - cytology; Muscle Fibers, Skeletal - drug effects; Muscle Fibers, Skeletal - metabolism; Myocardium - cytology; Nifedipine - pharmacology; Potassium - pharmacology; Rats; Rats, Wistar; Thyroxine - pharmacokinetics; Triiodothyronine - pharmacokinetics; Verapamil - pharmacology
• ISSN: 0363-6135; 1522-1539
• DOI: 10.1152/ajpheart.2001.281.5.H1985

Departments of 1  Internal Medicine III and 2  Biochemistry, Erasmus University Medical School, 3000 DR Rotterdam; and 3  Department of Veterinary Anatomy and Physiology, Utrecht University, 3508 TD Utrecht, The Netherlands The effects of the Ca 2+ channel blockers verapamil, nifedipine, and diltiazem on triiodothyronine (T 3 ) and thyroxine (T 4 ) uptake were tested in cultured cardiomyocytes from 2-day-old rats. Experiments were performed at 37°C in medium with 0.5% BSA for [ 125 I]T 3 (100 pM) or 0.1% BSA for [ 125 I]T 4 (350 pM). The 15-min uptake of [ 125 I]T 3 was 0.124 ± 0.013 fmol/pM free T 3 ( n  = 6); [ 125 I]T 4 uptake was 0.032 ± 0.003 fmol/pM free T 4 ( n  = 12). Neither T 3 nor T 4 uptake was affected by 1% DMSO (diluent for nifedipine and verapamil). Uptake of [ 125 I]T 3 but not of [ 125 I]T 4 was dose dependently reduced by incubation with 1-100 µM verapamil (49-87%, P