Comparative ultrastructural morphometric analysis of atrial specific granules in the bat, mouse, and rat

Abstract

Size, incidence, and volume density of atrial specific granules (ASG) in right atrial cells from five animals each of the rat (average weight 210 g), mouse (average weight 28 g), fruit-eating bat Megaloglossus woermanni (BMW; average weight 35 g), and the insect-eating bat Pipistrellus pipistrellus (BPP; average weight 6 g) have been compared via ultrastructural morphometry. In all three parameters of granule measurement, significantly higher figures were obtained in the rodents than in the bats. However, between the rat and the mouse, as also between the two species of bats, no significant differences were noted in any of the measurements. These results therefore do not support the prevalent view that the number and size of the granules decrease with increase in size of the animal species. The low content of ASG in atrial cells of the bats is probably an indication of low demand for the natriuretic hormone of the granule, because, in such animals, and particularly in flight, conservation of fluid and electrolytes is of paramount importance. This suggests that granule content is adapted to fluid and electrolyte regulation in relation to the functional capacity of the animal. We also observed ASG-like structures in endothelial cells of capillaries of bat tissue but not in rodents. The function of these granules or whether or not they represent atrial specific ones is not clear from the present study.

Ultrastructural Characteristics of Atrial, Ventricular and Subendocardial (Purkinje) Cells of the Fruit-Eating Bat <i>Eidolon helvum</i>

“…Foremost is the observation of a low concentration and small size of atrial granules. This strengthens our previous assertion [6] that granule size and concentration are adapted to fluid and electrolyte homeostasis and not to the size or weight of the animal, as suggested by Jamieson and Palade [5]. As reported by several workers including Currie et al [11], Forssmann et al 112].…”

“…Purkinje cells of this species are unique 94 Ayettey/Tagoe/Y ates Bat Myocardial Ultrastructure in that they are well endowed with mitochondria, and their myofibrils are well aligned though scanty in volume. In our study of the atrial myocardium of the insect eating bat P. pipistrellus and the fruit-eating bat M. woermanni [6], we drew attention to capillary endothelial gran ules that are different from the rod-shaped, tubular bodies described by Weibel and Paladc [10] in arterial endothelia and reported to contain von Willebrand protein [21]. In the present work, we encountered similar granules in endothe lial cell bodies in the atrial and ventricular endocardia of E. helvum but not in rodents.…”

“…[5]. Most likely, it has to do with fluid and electrolyte requirements of the animal [6], Subendocardial. Purkinje cells also are not alike in size and in myofibrillar content and organization among mammals [3] nor do they all lack T-tubule invaginations of the sarcolcmma |3 , 4,7,8].…”

Cardiomyocytes can be generated from marrow stromal cells in vitro

“…These differentiated CMG myotubes have a cardiomyocyte-like ultrastructure, including typical sarcomeres, a centrally positioned nucleus, abundant glycogen granules, a number of mitochondria, and many atrial granules. Tagoe et al (34) reported that the most common size of atrial granules observed in the adult mice atrium was 150-200 nm in diameter, but they also found that ∼35% of the atrial granules in adult mice atria ranged between 50 and 150 nm in diameter. The atrial granules observed in the differentiated CMG myotubes were 70-130 nm in diameter.…”

Morphometric Study of Specific Heart Granules in the Grey Seal (<i>Halichoerus grypus</i>)

“…Research in volving three species of bats compared with the rat has shown significant differences in atrial granule concentra tions [Ocansey et al. 1990: Ayettey et al. 1993: granule concentrations were significantly lower in atrial cells of all three species of bats (insect-eating, Pipistrellus pipistrellus and fruit-eating, Eidolon helvum and Megaloglossus woennanni) than in those of the rat.…”