Changes in nerve growth factor content of the submaxillary gland in the genetically dystrophic ( mdx) mouse

Abstract

We evaluated the nerve growth factor (NGF) contents in the submaxillary gland of the mdx mouse, a model for Duchenne muscular dystrophy (DMD), and found that the NGF and NGF mRNA contents in this organ, where extraordinarily high amounts of NGF are synthesized and stored independently of development or maintenance of the nervous system, were markedly elevated in the male mdx mouse at 8 and 11 weeks of age. However, the NGF content of this organ in 4-week-old male mdx mice was lower than that of control mice although statistical significance of difference was not observed. In the mdx female mouse, the submaxillary NGF content was significantly lower than that of the normal mouse at 4 weeks of age, but was similar to that of the normal at 8 and 11 weeks of age. The amounts of epidermal growth factor (EGF), another protein that is known to be sexually and developmentally regulated in the mouse submaxillary gland like NGF, was found to be also significantly increased in this organ of the male mdx mouse at 8 and 11 weeks of age, and to be significantly decreased in that of the female mdx mouse at 4 weeks of age. The parallel changes in NGF and EGF contents during development of the submaxillary gland suggest that the mdx mouse suffers from some abnormality in the development of this organ. The concentration of serum thyroxine (T4) was significantly reduced in afflicted males and females during the period examined (from 4 to 11 weeks after birth); and that of serum testosterone was significantly reduced in 4-week-old male mdx mice, but no significant differences were observed in 8- or 11-week-old afflicted males or 4- to 11-week-old afflicted females. These results suggest that the abnormality in the development of the submaxillary gland in the mdx mouse is due to the abnormalities of these hormone levels.