Raman Investigation of Cardiac Tissues with Sodium-Induced High Stiffness

This study investigates the molecular and mechanical effects of sodium accumulation in myocardial tissue using a combination of physiological measurements and Raman spectroscopy. Male Wistar rats were maintained on normal- and high-salt diets to induce differential sodium loading in cardiac tissue. Hemodynamic and mechanical analyses revealed increased myocardial stiffness and altered contractile parameters in the high-salt group. Raman microspectroscopy of myocardial sections demonstrated distinct spectral changes, particularly in regions corresponding to glycosaminoglycan (GAG), collagen, and its component, proline. Enhanced Raman signals near 1640 cm^-1 in the Amide I range, 1246 cm^-1 in the Amide III range, and in the 1030-1070 cm^-1 range indicated structural modifications of the GAG-collagen complex and an increased contribution of proline-rich collagen, consistent with elevated tissue rigidity. These findings support the concept that sodium deposition in the myocardium alters its molecular architecture and mechanical properties through GAG-mediated binding and collagen remodeling. This study provides new insights into the biophysical mechanisms linking sodium homeostasis to myocardial stiffness and diastolic dysfunction.