Expression of high activity of ornithine decarboxylase and occurrence of unusual chromophobic cells in anterior pituitary gland of a novel growth-retarded strain of mice, grm/grm.

Extremely high activity of ornithine decarboxylase (ODC) was detected in the pituitary gland of growth-retarded mice, grm/grm at 2 months after birth. The elevated enzyme activity gradually decreased to the control level in 14 months after birth. In the pituitary gland of the growth-retarded mice, unusual chromophobic cells were also present from the early stages after birth. The chromophobic cells showed conspicuous proliferations and resulted in a distinct hyperplasia of the tissue after 4 months after birth. These findings suggest that ODC is correlated to the progressive transformation of pituitary cells into the chromophobic cells.