Morphometric study of ventricular myocardial cells in the bat (Pipistrellus pipistrellus), hamster (Mesocricetus auratus) and Wistar rat.

A comparative morphometric study of ventricular myocardial cells of the West African insect-eating the Pipistrellus pipistrellus, the hamster and the rat revealed significant differences in volume fractions of mitochondria myofibrils, lipid bodies and T tubules. In the cells of the bat, mitochondria constitute 35% of cytoplasmic volume compared with 29 and 30% in the hamster and rat, respectively. Notably, crista density is much higher in the bat cells (3.58 x 10(5) cm-1) than in those of the hamster (2.59 x 10(5) cm-1) and of the rat (2.48 x 10(5) cm-1). Myofibril concentration is 40% in the bat, 53% in the hamster and 55% in the rat. There is greater numerical density of lipid bodies in the bat (212.27 x 10(9) cm-3) than in the hamster (139.20 x 10(9) cm-3) and in the rat (114.00 x 10(9) cm-3). The volume occupied by T tubules is 0.02 in the bat and hamster, and 0.009 in the rat. These differences suggest structural design for efficient metabolic activity in the bat which, among mammals, has high exercise tolerance.