Normal size of the lumen of the aorta in dwarf mice lacking IGF-II.

The peptide insulin-like growth factor II (IGF-II) is a foetal promoter of growth and differentiation. Genetically modified mice have provided insights into the contribution of IGF-II to the determination of the size of the body and individual organs. Nevertheless, the role of IGF-II in regulating the size of major blood vessels is poorly understood. Here, the transverse luminal and medial area of the aorta and the number of medial cell nuclei are shown not to be significantly different in adult wild-type and Igf2 nullizygous mice, despite a approximately 30% reduction in BW in the latter group. The observations in this study suggest that IGF-II is not an indispensable factor in the determination of the size of the aortic lumen, and are consistent with the view that growth factor redundancy may be a safeguard mechanism to maintain the size of the aorta within a range compatible with viability. Copyright 2001 Harcourt Publishers Ltd.