Quantitative studies on the ultrastructural differentiation and growth of mammalian cardiac muscle cells. II. The atria and ventricles of the guinea pig
Hirakow, R.; Gotoh, T.
Acta Anatomica 108(2): 230-237
1980
ISSN/ISBN: 0001-5180 PMID: 7405540 Document Number: 163351
The guinea pig is a nest-quitter or nidifugous mammal which develops almost to the weaning stage before birth. Myocardial cells of the bilateral atria and ventricles of guinea pigs were examined for comparison with the rat by an ultrastructural quantitative method during the pre- and postnatal developmental periods, at copulation ages of 50, 57, 64 (term), 73 and 80 days. Throughout the developmental stages, no clear differences between right and left sides were found in the characteristics of the myocardial cells. At day 57, T-tubules were first recognized in the ventricular muscle cells, and at the same time the fiber thickness of the ventricular muscle cells (8-9 .mu.m) became greater than that of the atrial cells (6-7 .mu.m). At this stage the fraction of mitochondria differed between the atrial and ventricular muscle cells. The general cellular features appeared to change more during the last prenatal week from copulation day 57 to day 64 (term) than during the 1st postnatal week. The last prenatal week in the ontogeny of the guinea pig heart may correspond to the postnatal period from the 10th to the 20th day in the ontogeny of the rat heart.