muramidase and Myocarditis

We previously showed that lysozyme (Lzm-S), derived from leukocytes, caused myocardial depression in canine sepsis by binding to the endocardial endothelium to release nitric oxide (NO). NO then diffuses to adjacent myocytes to activate the cGMP pathway. In a canine right ventricular trabecular (RVT) preparation, Lzm-S also decreased the inotropic response to field stimulation (FSR) during which the sympathetic and parasympathetic nerves were simulated to measure the adrenergic response. In the present study, we determined whether the pathway by which Lzm-S decreased FSR was different from the pathway by which Lzm-S reduced steady-state (SS) contraction. Furthermore, we determined whether the decrease in FSR was due to a decrease in sympathetic stimulation or enhanced parasympathetic signaling. In the RVT preparation, we found that the inhibitory effect of Lzm-S on FSR was prevented by NO synthase (NOS) inhibitors. A cGMP inhibitor also blocked the depressant activity of Lzm-S. However, in contrast to the Lzm-S-induced decline in SS contraction, chemical removal of the endocardial endothelium by Triton X-100 to eliminate endothelial NO release did not prevent the decrease in FSR. An inhibitory G protein was involved in the effect of Lzm-S, since FSR could be restored by treatment with pertussis toxin. Atropine prevented the Lzm-S-induced decline in FSR, whereas beta(1)- and beta(2)-adrenoceptor function was not impaired by Lzm-S. These results indicate that the Lzm-S-induced decrease in FSR results from a nonendothelial release of NO. NO then acts through inhibitory G protein to enhance parasympathetic signaling.

Topics: Animals; Dogs; Electric Stimulation; Endothelium, Vascular; GTP-Binding Proteins; Muramidase; Myocarditis; Nitric Oxide; Receptors, Adrenergic, beta; Sepsis; Signal Transduction; Sympathetic Nervous System

Topics: Antistreptolysin; Child; Complement System Proteins; Humans; Immunoglobulins; Muramidase; Myocarditis; Rheumatic Heart Disease

Giant cell myocarditis (GCM) as a distinct disease entity has been questioned. The superficial morphologic resemblance to cardiac sarcoidosis and incomplete histopathologic assessment of extracardiac organ systems in reported cases has suggested that GCM represents a predominant cardiac manifestation of generalized sarcoidosis. The morphologic and immunocytochemical features at autopsy of this rare disorder were seen in a 15-year-old boy. All other organs were free of granulomatous inflammation. Transition from normal myocardial fibers to giant cells was observed, without a limiting plasma membrane between the two different aspects of the fiber. Immunocytochemistry for cytoplasmic muramidase (CM) showed CM in neutrophils and tissue macrophages. Cytoplasmic muramidase was distinctly absent from the characteristic giant cells. The classification of GCM as a disease separate from generalized sarcoidosis may be justified.

Topics: Adolescent; Diagnosis, Differential; Granuloma, Giant Cell; Humans; Immunoenzyme Techniques; Male; Microscopy, Electron; Muramidase; Myocarditis; Myocardium; Sarcoidosis

Topics: Child; Child, Preschool; Complement System Proteins; Humans; Immunity, Innate; Immunoglobulin A; Immunoglobulin G; Immunoglobulin M; Muramidase; Myocarditis; Properdin