In acute experiments on rats, systemic inflammation was induced by intraperitoneal E. coli lipopolysaccharide (LPS) injection that in a dose of 5 microg/kg caused an increase in rectal temperature by 1.0 +/- 0.3 degrees C and 2.5 +/- 0.2 degrees C, respectively, at thermobox temperature of 22 degrees C and 35 degrees C, and in a dose of 1000 microg/kg caused its decrease by 1.7 +/- 0.6 degrees C at 22 degrees C and increase by 0.4 +/- 0.1 degrees C at 35 degrees C. In all the animals, cardiomyocytes demonstrated a functional tension which appeared as a growing number of mitochondria, nuclear pores and cisterns of the endoplasmic reticulum. In the microvessels, when both LPS doses were administered, leukocyte and macrophage adhesion to endotheliocyte membrane was demonstrated. After LPS injection in a dose of 1000 microg/kg, numerous large secretory granules were observed under the sarcolemma close to the microvessels in hormone-producing cardiomyocytes, containing natriuretic hormone. Contractile cardiomyocytes showed signs of early-stage apoptosis (accumulation of small mitochondria with electrone dense matrix, cytoplasmic invagination into the nucleus, formation of apoptotic bodies). LPS in a dose of 1000 microg/kg at thermobox temperature of 35 degrees C induced changes in some cardiomyocytes with the signs of late-stage apoptosis (condensed nucleus and cytoplasm).