Overproduction of amyloid β protein (Aβ) derived from amyloid β protein precursor (βAPP) is one of the cause of Alzheimer's disease. To produce animal model to overexpress Aβ, we generated three sets of mice expressing the transgene of carboxyl-terminal fragments (CTF) of βAPP (signal peptide and 99 residues of CTF for βANORβ, methionine and 103 residues of CTF for βAΔNORβ, and methionine and 103 residues of CTF with substitution of Swedish type mutation for βAΔNLβ) under control of the cytomegalovirus enhancer/chicken β-actin promoter. The transgenic protein was detected as 11.4 kD CTF in βANORβ, and as 11.8 kD CTF in βAΔNORβ and βAΔNLβ. The expression of the transgene was detected from many organs, but the amount of mRNA, CTF, and Aβ did not correlate well. In βANORβ, Aβ was detected in brain, kidney, plasm and pancreas. In the pancreas, there was much deposition of Aβ with severe degeneration of pancreatic acinar cells and infiltration of macrophages. Examination of these cells by electron microscopy revealed many putative amyloid fibrils (7-12 nm) that were stained by anti-Aβ antibodies. In βAΔNLβ, Aβ was deposited in neurons of cerebral cortex and hippocampus. Electromicroscopically, there was intracellular deposition of dense substances that were stained by anti-Aβ antibodies in these neurons. Our findings indicate that tissue-specific posttranslational processing may play a pivotal role in Aβ production, and that the Swedish type mutation may accelerate Aβ deposition in neurons in vivo.