Alterations in myocardial connexin-43 and matrix metalloproteinase-2 signaling in response to pregnancy and oxygen deprivation of Wistar rats: a pilot study

Two important aspects of cardiac adaptive response to pregnancy have been studied in normal as well as hypoxic conditions: (1) intercellular signaling mediated by myocardial connexin-43 (Cx43) that is crucial to synchronize heart function; (2) extracellular signaling mediated by matrix metalloproteinase-2 (MMP-2) that is an early marker of extracellular matrix remodeling. Myocardial Cx43 distribution and functional capillary density were determined as well. Hypoxia was induced by exposure of rats to 10.5% O2 and 89.5% N2 in a hermetically sealed chamber. Findings showed that pregnancy resulted in a significant increase of Cx43 protein expression, its functional phosphorylated forms, and enhanced capillary density while did not affect either expression of total MMP-2 or its activity. Maternal hypoxia for 12 or 16 h did not affect elevated Cx43 but enhanced its distribution on lateral sides of the cardiomyocytes. In contrast, hypoxia of nonpregnant rats resulted in upregulation of Cx43, its lateral distribution, and enhanced capillary density. Hypoxia did not affect myocardial MMP-2 either in pregnant or nonpregnant rats. Cardiac adaptive response to pregnancy is accompanied by enhanced Cx43 without changes in MMP-2 signaling. Pregnant rat heart is tolerant to short-term hypoxemia, while nonpregnant rat heart reacts by upregulation of Cx43 and increased capillary density.