The growth of different organs of normal and dwarfed Snell mice, before and during growth hormone therapy

Abstract

Abstract. This study was performed in order to obtain more insight in the relationship between the growth of different organs of normal Snell mice and their dwarfed littermates before and during growth hormone therapy. Beside body weight the weights of the following organs were studied: liver, kidneys, heart, the muscles quadriceps femoris and gastrocnemius, submandibular salivary glands, testes, epididymal fatpads, thymus, spleen and skinfold thickness. The data show that, similar to body weight, growth of these organs in dwarf mice is arrested at approximately 2½ weeks of age, after which little further growth occurs, leaving their absolute weight far below normal. Related to body weight the liver is close to normal, lower values are obtained for the heart and very low ones for the kidneys, the lymphoid organs, thymus and spleen, and the epididymal fatpads. At two weeks of age the weight of the brain is only slightly less than normal, but gradually stays behind until it is only 2/3 of normal at the age of 17 weeks. Due to the small weight of the dwarfs the contribution to body weight of the brain is higher than normal. Growth hormone, after 4 weeks of treatment, had induced significant growth of all organs studied, except for the testes and the thickness of the skinfold. After 10 weeks of treatment all organ weights were significantly increased. Growth was most marked in the lymphoid organs, spleen and thymus, and the epididymal fatpads (155–173% of controls). The submandibular salivary glands and the testes increased more than body weight (respectively 141 and 136% vs. 123%). Increase proportional to body weight was found for the muscles quadriceps femoris and gastrocnemius, heart, liver and kidneys. In contrast, increase of the brain (106%) and skinfold (111%) was much lower.