Physiological contractility of cardiomyocytes in the wall of mouse and rat azygos vein.

We recently demonstrated the abundant presence of cardiomyocytes in the wall of thoracic veins of adult mouse and rat. The highly differentiated morphology and myofilament protein contents of the venous cardiomyocytes suggested contractile functions. Here we further investigated the contractility of mouse and rat azygos venous rings compared with that of atrial strips and ventricular papillary muscle. 5-Bromo-4-chloro-indolyl-galactopyranoside (X-gal) staining of transgenic mouse vessels expressing lacZ under a cloned cardiac troponin T promoter demonstrated that the venous cardiomyocytes are discontinuous from atrial myocardium and aligned in the wall of thoracic veins perpendicular to the vessel axis. Histological sections displayed sarcomeric striations in the venous cardiomyocytes, which indicate an encirclement orientation of myofibrils in the vessel wall. Mechanical studies found that the rings of mouse and rat azygos vein produce strong cardiac type twitch contractions when stimulated with electrical pacing in contrast to the weak and slow smooth muscle contractions induced using 90 mM KCl. The twitch contraction and relaxation of mouse azygos veins further exhibited a cardiac type of ß-adrenergic responses. Quantitative comparison showed that the contractions of venous cardiomyocytes are slightly slower than those of atrium muscle but significantly faster than those of ventricular papillary muscle. These novel findings indicate that the cardiomyocytes abundant in the wall of rodent thoracic veins possess fully differentiated cardiac muscle phenotype despite their anatomical and functional segregations from the heart.

Formation of the azygos vein / Formación de la vena ácigos

The aim of the present study was to determine the most common origin of the azygos vein. Thirty cadavers male and female, white and non-white adult individuals of different ages fixed in 10 percent formaldehyde and dissected. All cadavers had an undisclosed clinical death and were donated to the Universidade Estadual de Ciências da Saúde de Alagoa s, Brazil. Eleven different formations were found. The right subcostal vein was was only observed in 13 cases (43.33 percent); the azygos vein was formed by the confluence of the right subcostal and right ascending lumbar vein in three cases (10 percent); by the right subcostal vein with a contribution from the inferior vena cava (IVC) in three cases (10 percent); by the right subcostal with contribution from IVC and right ascending lumbar vein in three cases (10 percent); by the right and left subcostal veins in two cases (6.66 percent); by the right and left subcostal veins and contribution from the IVC in one case (3.33 percent); by the right and left subcostal veins and left accessory renal vein in one case (3.33 percent); by the left renal vein in one case (3.33 percent); by the right subcostal and left gonadal veins with contribution from the IVC in one case (3.33 percent); by the right subcostal and left renal veins in one case (3.33 percent); and composed by the continuation of the 11th posterior intercostal vein in one case (3.33 percent). Based on the results, the right subcostal vein was the only structure with a significant presence in the formation of the azygos vein.

El objetivo del estudio fue verificar cual es la disposición más frecuente del origen de la vena ácigos. Fueron disecados 30 cadáveres de individuos adultos, de ambos sexos, de diferentes grupos étnicos, fijados en formaldehído al 10 por ciento, donados a la Universidade Estadual de Ciencias da Saúde de Alagoas. Se encontraron 11 formaciones diferentes. En 13 casos (43,33 por ciento) se observó sólo la vena subcostal derecha; en 3 casos (10 por ciento) la vena ácigos estaba formada por la confluencia de las venas subcostal derecha y lumbar ascendente derecha; en 3 casos (10 por ciento) formado por las venas subcostal derecha y una contribución de la vena cava inferior VCI; en 3 casos (10 por ciento) por las venas subcostal derecha y contribución de la VCI y lumbar ascendente derecha; 2 casos (6,66 por ciento) por las venas subcostales derecha e izquierda; en 1 caso (3,33 por ciento) por las venas subcostal derecha, izquierda y contribución de la VCI; en 1 caso (3,33 por ciento) por las venas subcostal derecha e izquierda y renal accesoria izquierda; en 1 caso (3,33 por ciento) por la vena renal izquierda; en1 caso (3,33 por ciento) por las venas subcostal derecha, gonadal izquierda y contribución de la VCI; en 1 caso (3,33 por ciento) por las venas subcostal derecha y renal izquierda y en 1 caso (3,33 por ciento) por la continuación de la 11 vena intercostal posterior. Con base en los resultados podemos concluir que la vena subcostal derecha fue la única estructura con presencia significativa en la formación de la vena ácigos.