Morphometric Analysis of Flexor Carpi Radialis and Flexor Digitorum Muscles in Normal Young Wistar Rats

Normative muscle fiber morphometrics serve as a reference to assess injuries and the response to different treatments and as well as physiological adjustments that occur in sports or during the aging process. Animal models using rats are common, but data on muscle morphometrics are scarce. The purpose of this study was to determine the morphometrics of the flexor carpi radialis (FCR) and flexor digitorum (FD) muscles in normal Wistar rats. Experimental study approved by the animal use ethics committee (n. 030/2016). Eight female Wistar rats eight weeks of age were used. The muscles were fixed, dehydrated, and embedded in Paraplast®. The cuts were stained with hematoxylin and eosin and photomicrographed. The analysis was performed using the ImageJ program, with the determination of the area, perimeter, Feret’s diameter, and number of muscle fibers in 10% of the frames (magnification: 40 x). Descriptive data analysis was performed. The average number of muscle fibers was 437 ± 138 for the FCR and 546 ± 232 for FD. Average perimeter, diameter, and area of the FCR muscle fibers were 74.42 ± 12.62 µm, 27.35 ± 5.26 µm, and 387.66 + 133.57 µm2, respectively. These figures were 76.73 ± 14.84 µm, 28.62 ± 6.23 µm, and 411.22 ± 155.50 µm2, respectively, for the FD muscle fibers. These results are important, especially for experimental studies involving the thoracic limb of rats for comparisons to normative reference values.