title: Effect of thyroid state on cardiac myosin P-light chain phosphorylation during exercise.
abstract: This study ascertained the effects of thyroid deficiency (TD) and hyperthyroidism (H) on in vivo cardiovascular functional capacity in the context of cardiac myosin light chain 2 phosphorylation [P-LC(P)], a proposed modulator of myocardial function, at rest and during exercise. Compared with normal controls (NC), Ca2(+)-regulated myofibril adenosinetriphosphatase was reduced by 39% in TD and increased by 9% in H rats. This response was associated with a 20-fold increase in the V3 isoform and an 11% increase in the V1 isoform in TD and H rats, respectively. Submaximal treadmill exercise elicited significant elevations in all myocardial functional indexes examined in H rats compared with the NC group, whereas the opposite occurred for the TD group. Despite the marked contrast in cardiac function among the three groups, intrinsic levels of P-LC(P) were similar at rest among the groups and were significantly reduced in both TD and H groups relative to controls during exercise. These data suggest that although thyroid state exerts a profound impact on intrinsic myocardial functional state, it exerts little control over cellular processes regulating P-LC(P) during rest and exercise.
authors: Department of Physiology and Biophysics, University of California, Irvine 92717.
authors: D P
authors: DP
authors: Fitzsimons
authors: P W
authors: PW
authors: Bodell
authors: R E
authors: RE
authors: Herrick
authors: K M
authors: KM
authors: Baldwin
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D005260:Female; D006439:Hemodynamics / Q000502:physiology; D006980:Hyperthyroidism / Q000503:physiopathology; D007037:Hypothyroidism / Q000503:physiopathology; D009200:Myocardial Contraction / Q000502:physiology; D009206:Myocardium / Q000378:metabolism*; D009218:Myosins / Q000378:metabolism*; D010766:Phosphorylation; D005082:Physical Exertion / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D013961:Thyroid Gland / Q000502:physiology*
chemical_list: D000251:Adenosine Triphosphatases; D009218:Myosins