title: Short-term administration of insulin-like growth factor I (IGF-1) does not induce myocardial IGF-1 resistance.
abstract: The advent of recombinant technology has revealed attractive therapeutic profile of insulin-like growth factor I (IGF-1) in the treatment of chronic cardiovascular diseases such as diabetes and heart failure. However, the safety and potential adverse effect of IGF-1 have not been well defined. This study was designed to evaluate the impact of short-term IGF-1 administration on myocardial contractile function. Adult rats were given recombinant human IGF-1 (3mg/kg/d, s.c.) for 8 weeks. Mechanical properties were evaluated in left-ventricular papillary muscles using a force-transducer. Myocardial contractile properties analyzed included peak tension development (PTD), time-to-peak tension (TPT), time-to-90% relaxation (RT(90)), and maximal velocity of tension development/decline (+/-VT). Short-term IGF-1 treatment enhanced the plasma IGF-1 level but had no effect on body and organ weights. The myocardium from IGF-1-treated rats exhibited enhanced PTD associated with similar TPT, RT(90), and +/-VT compared to the control group. IGF-1-treated myocardium exhibits an enhanced PTD-Ca(2+) response and a better intracellular Ca(2+) replenishing ability at the low stimulus frequencies. Acute application of IGF-1 (1-500 ng/ml) elicited a comparable concentration-dependent increase in PTD in myocardium from both control and the IGF-1-treated groups. Acute IGF-1 application had no effect on +/-VT, TPT, and RT(90) in either group tested. Pretreatment with the nitric oxide synthase inhibitor N omega-nitro-L-arginine methyl ester blunted the IGF-1-induced positive response in myocardium from both control and IGF-1-treated groups. These results suggest that short-term IGF-1 treatment is unlikely to induce IGF-1 resistance in myocardial contractile function.
authors.affiliation: Department of Pharmacology, Physiology and Therapeutics, University of North Dakota School of Medicine, Grand Forks, ND 58203, USA. jren@medicine.nodak.edu
authors.forename: Jun
authors.initials: J
authors.lastname: Ren
mesh_terms: D000818:Animals; D002118:Calcium / Q000008:administration & dosage; D004351:Drug Resistance; D004558:Electric Stimulation; D006321:Heart / Q000187:drug effects*; D006331:Heart Diseases / Q000188:drug therapy; D006801:Humans; D066298:In Vitro Techniques; D007328:Insulin / Q000008:administration & dosage; D007334:Insulin-Like Growth Factor I / Q000008:administration & dosage* / Q000633:toxicity; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects; D010210:Papillary Muscles / Q000187:drug effects / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins / Q000008:administration & dosage / Q000633:toxicity; D016277:Ventricular Function, Left / Q000187:drug effects
chemical_list: D007328:Insulin; D011994:Recombinant Proteins; D007334:Insulin-Like Growth Factor I; D002118:Calcium