Striated myocytes and atrial specific granules in the pulmonary veins of chronically infarcted rat hearts

Abstract

The ultrastructure of the striated myocytes in the pulmonary myocardium of the Wistar rat, was studied following left ventricular infarction (LVI) for 4 days and 4 weeks, respectively. Ischemia was provided by ligating of the left coronary artery which successively produces left ventricular dysfunction and congestion of the left atrium and pulmonary veins. In general, the striated myocytes of the extrapulmonary veins of the control groups displayed ultrastructural characteristics similar to those of the left atrium. However, in the former, transverse tubules commonly occurred making interior couplings with the SR at the I-band levels. Also, between striated myocytes of the intrapulmonary veins of the controls nexus-like junctions of about 2 micron length were observed. Further, in the same groups atrial specific granules (ASG), including A-granules and B-granules, were present in about 20%-30% of the striated myocytes of the extrapulmonary veins as shown in single sections. The ASG tended to decrease by number in areas approaching the lung hilus and were not observed in the intrapulmonary veins of the controls. After 4 days of ventricular ischemia granules also appeared in the intrapulmonary veins. They were mostly seen in single and randomly spread in the cytoplasm of a limited number of cells, i.e., in between 0% and 5% of the myocytes as seen in single sections. Four days of LVI produced only minor cellular injuries to the extrapulmonary and intrapulmonary venous wall, while more severe lesions appeared in both areas following 4 weeks of LVI. Such lesions were preferably localized to the adluminal surface and consisted mainly of Z-band and sarcomere anomalies, vacuolization of the cytoplasm and mitochondrial swelling.

Immunohistochemical localization of ANP in the pulmonary veins of the rat.

“…In general, the latter myocytes displayed moderate granular staining, and, the staining appeared to be more evenly distributed in the cytoplasm than found in the left atrium. The present findings are comparable to previous studies regarding the presence of ASG in the pulmonary myocardium of the rat (14). In the latter study, both A-granules and B-granules were observed in the extrapulmonary veins, whereas, in the intrapulmonary veins ASG were only present at limited numbers after congestion of the left atrium and the pulmonary veins following left ventricular infarction.…”

“…The striated myocytes are structurally similar to those found in the atrium. Also, "atrial specific granules" (ASG) have been reported to be present in some of the myocytes of the extrapulmonary portion of the veins (14). These specific granules, including A-granules and B-granules (2), are morphologically similar to the ASG of the atria.…”

Cardiac-like musculature of the intrapulmonary venous wall of the long-clawed shrew (Sorex unguiculatus), common tree shrew (Tupaia glis) and common marmoset (Callithrix jacchus)

“…A small quantity of AGs in the intrapulmonary venous myocytes have been reported in rodents (Larsen et al, 1987b;Toshimori et al, 1988;Endo et al, 1992b). The present immunohistochemical data suggest that the cardiac-like musculature of the pulmonary venous system may have an endocrine function of ANP in tree shrews as well as in rodents.…”

Immunocytochemical localization of atrial natriuretic peptide in the venae cavae and the pulmonary veins of the rat

“…Correspondingly, the myocardium of the left atrium continues into the pulmonary veins (Ludatscher, 1968; 0018-2214/88 $03.00 +.12 © 1988 Chapman and Hall Ltd. Paes de Almeida et al, 1975;Jarkovska, 1985;Larsen et al, 1987b). In the pulmonary myocardium, the striated myocytes have been shown to contain ASG (Larsen et al, 1987b). Further, in a recent study (Larsen et al, 1987a) we demonstrated the presence of ANP in the same tissue by immunohistochemical staining.…”

“…While the right atrial myocardium of rodentia extends almost to the top of the superior vena cava, it contributes to a considerable shorter segment of the inferior vena cava. Correspondingly, the myocardium of the left atrium continues into the pulmonary veins (Ludatscher, 1968; 0018-2214/88 $03.00 +.12 © 1988 Chapman and Hall Ltd. Paes de Almeida et al, 1975;Jarkovska, 1985;Larsen et al, 1987b). In the pulmonary myocardium, the striated myocytes have been shown to contain ASG (Larsen et al, 1987b).…”