Comparative study on the growth patterns of internal organs of male and female mice at three stages of development

Abstract

This study investigated the growth of various organs in 36 male and 36 female mice using increase in weight as the index of growth. The mice were randomly selected from the offspring of the same breeding stock. They were given a commercially prepared diet and drinking water ad libitum until they were sacrificed at 3, 6 and 12 weeks of age. At each age, 12 males and 12 females were sacrificed by decapitation at the atlanto-occipital joint. The live body weight of each mouse was determined using a mettler top-loader weighing machine. Following death, skeletal muscles (triceps brachii and gastrocnemius muscles) and some internal organs (lungs, heart, kidneys, liver and spleen) were dissected and their weights were determined using a mettler beam balance. Humerus and femur were also dissected from each mouse and their lengths were determined using a venier caliper. The muscle mass index (milligram muscle weight per gram body weight) was calculated for each of these muscles. The Relative Organ Weight (ROW), expressed as percentage of body weight contributed by each internal organ was calculated. The muscle mass indices of the muscles of male and female mice were not significantly different (p>0.05) at 3 weeks of age. However, at 6 and 12 weeks of age, there were significant differences in the muscle mass indices of biceps brachii (p<0.01) and gastrocnemius (p<0.05) muscles of male and female mice. There were no significant differences (p>0.05) between the relative weights of organs of male and female mice at 3 weeks of age. The relative weights of the heart (p<0.05), liver (p<0.01), spleen (p<0.05) and kidneys (p<0.01) were significantly greater in the males at 6 weeks of age. At 12 weeks of age, the relative weights of the heart (p<0.05) and the kidneys (p<0.01) remained significantly greater in the male mice, but the relative weights of the lungs (p<0.05) and the spleen (p<0.01) were significantly greater in females. The study therefore, demonstrated that although sex differences were not evident in the relative weights of these organs at 3 weeks of age, there were sex differences in the body weights and growth patterns of muscles, bones and internal organs of male and female mice at 6 weeks and 12 weeks of age. It was suggested that these sex differences might have arisen from the possible significant influence of sex hormones on the growth and development of these organs in both male and female mice.

KEY WORDS: Mice, organs, growth, sex differences

Nigerian Veterinary Journal Vol.24(2) 2003: 10-18