MORPHOLOGICAL AND MORPHOMETRIC STUDY OF ATRIAL SPECIFIC GRANULES AND OTHER SECRETORY COMPONENTS IN DOGS EXPERIMENTALLY INFECTED WITH TRYPANOSOMA-CRUZI

Changes in blood volume can induce morphometric and morphological alte rations in the secretory complex of the myoendocrine cells due to the stretching of atrial walls. These alterations were studied by electron microscopy, using dogs infected intraperitonially with Trypanosoma cr uzi and necropsied during the acute phase of the infection when conges tive heart failure was present. Several changes were observed in the m yoendocrine cells of the heart: hypertrophy and hyperplasia of rough e ndoplasmic reticulum and Golgi complex, increase in telenuclear secret ory complex, increase in fusion of type B atrial specific granules (AS G), decrease of the total number of ASG, enlargement of the maximum di ameter of type A ASG and a relative increase in the number of type B A SG. These alterations suggest a larger secretory activity of the atria l myoendocrine cells with a larger secretion of atrial natriuretic pep tide (ANP).