Jesus F Dominguez1, Sandra Howell. 1. Department of Biokinesiology, University of Southern California, 1540 E. Alcazar Street, CHP-155, Los Angeles, CA 90089, USA. jdomingu@usc.edu
Abstract
UNLABELLED: An analytic method based on simulation and modeling of long-term 45Ca(2+) efflux data was used to estimate steady-state Ca(2+) contents (nmolCa(2+)g(-1)tissuewetwt.) and exchange fluxes (nmolCa(2+)min(-1)g(-1)tissuewetwt.) for extracellular and intracellular compartments in in vitro resting diaphragm from congestive heart failure (CHF, n=12) and sham-operated (SHAM, n=10) rats. Left hemidiaphragms were excised from experimental animals, loaded with 45Ca(2+) for 1h, and washed out with 45Ca(2+)-free perfusate for 8h. Tissue from the right hemidiaphragm was used to assess single-fiber cross-sectional area (CSA) as well as the relative proteolytic activity of Ca(2+)-dependent calpain. Kinetic analysis of 45Ca(2+) efflux data revealed that CHF was associated with increased Ca(2+) contents of extracellular and intracellular compartments as well as increased Ca(2+) exchange fluxes for all compartments. This accounted for the model prediction of a 250% increase in total diaphragm Ca(2+). Furthermore, single-fiber CSA was decreased 12% and proteolytic activity of calpain was increased twofold in CHF diaphragm relative to SHAM. CONCLUSIONS: The kinetic data are consistent with the hypothesis that diaphragm Ca(2+) overload in CHF required all intercompartmental Ca(2+) fluxes to increase. The potential relationships among Ca(2+) overload, increased activity of calpain, and wasting of the diaphragm in CHF are discussed.
UNLABELLED: An analytic method based on simulation and modeling of long-term 45Ca(2+) efflux data was used to estimate steady-state Ca(2+) contents (nmolCa(2+)g(-1)tissuewetwt.) and exchange fluxes (nmolCa(2+)min(-1)g(-1)tissuewetwt.) for extracellular and intracellular compartments in in vitro resting diaphragm from congestive heart failure (CHF, n=12) and sham-operated (SHAM, n=10) rats. Left hemidiaphragms were excised from experimental animals, loaded with 45Ca(2+) for 1h, and washed out with 45Ca(2+)-free perfusate for 8h. Tissue from the right hemidiaphragm was used to assess single-fiber cross-sectional area (CSA) as well as the relative proteolytic activity of Ca(2+)-dependent calpain. Kinetic analysis of 45Ca(2+) efflux data revealed that CHF was associated with increased Ca(2+) contents of extracellular and intracellular compartments as well as increased Ca(2+) exchange fluxes for all compartments. This accounted for the model prediction of a 250% increase in total diaphragm Ca(2+). Furthermore, single-fiber CSA was decreased 12% and proteolytic activity of calpain was increased twofold in CHF diaphragm relative to SHAM. CONCLUSIONS: The kinetic data are consistent with the hypothesis that diaphragm Ca(2+) overload in CHF required all intercompartmental Ca(2+) fluxes to increase. The potential relationships among Ca(2+) overload, increased activity of calpain, and wasting of the diaphragm in CHF are discussed.
Authors: Bumsoo Ahn; Philip D Coblentz; Adam W Beharry; Nikhil Patel; Andrew R Judge; Jennifer S Moylan; Charles W Hoopes; Mark R Bonnell; Leonardo F Ferreira Journal: Front Physiol Date: 2017-01-09 Impact factor: 4.566