Structural, functional and metabolic remodeling of rat left ventricular myocytes in normal and in sodium-supplemented pregnancy

Abstract

Pregnancy is an important physiological condition associated with hemodynamic and endocrine changes that affect the heart. Nevertheless, very little is known about cardiomyocyte remodeling in this condition. Here, we studied the morphological, functional and metabolic remodeling of rat left ventricular myocytes that occurs in late stages of normal pregnancy (P) and in experimental preeclampsia induced by elevated (0.9%) sodium intake (P0.9). We applied confocal microscopy to examine the morphology and the contractility of single cells, while the patch clamp technique was used to assay ionic currents. Our results revealed a significant increase in the volume of single left ventricular cardiac myocytes in P, mainly resulting from cell elongation. In P0.9, further increase in the cell length led to a significant rise in the length/width ratio. Cell contractility was significantly decreased in glucose-based solutions in response to stimulation at 0.5 Hz and 6 Hz in P as well as in P0.9. The density of L-type calcium current (I(Ca)L) was not significantly altered in P or in P0.9. Metabolic substrates lactate and pyruvate, increased in the blood of P and P0.9 rats, enhanced contractility in P, without affecting I(Ca)L. The same effect, present but blunted in P0.9, was associated with a significant increase in I(Ca)L. Our results demonstrate that processes of adaptive remodeling take place in normal pregnancy, while maladaptive components are identified in experimental preeclampsia; they also reveal an adaptation in the use of energy substrates in pregnancy and its impairment by sodium supplementation.