DIETARY RESTRICTION MAINTAINS THE BASAL RATE OF SOMATOTROPE RENEWAL IN LATER LIFE IN MALE RATS

We investigated the impact of dietary restriction on the basal rate of somatotrope renewal in the pituitary gland, Bromodeoxyuridine (BrdU), a thymidine analog, was administered continuously for 1 week in male F344 rats at 3, 8 and 20 months of age (mo), fed ad libitum (AL) or di et restricted from 1.5 mo (BR), Combined immunostainings for BrdU and GH visualized newly formed somatotropes as well as pituitary cells in tissue sections, The rate of incorporation of BrdU by anterior pituita ry cells (BrdU-labeled nuclei/100 nuclei) was not influenced by the di etary regimen or age. The fraction of BrdU-labeled somatotropes relati ve to all labeled cells precipitously decreased to the same level in b oth dietary groups between 3 and 8 mo, although the fraction was great er in DR rats at 3 mo, In AL rats, the fraction decreased further betw een 8 and 20 mo, while it stabilized in DR rats, Our results suggested that dietary restriction maintains the basal rate of somatotrope rene wal in later life in male rats, Although one must also estimate the ef fects of dietary restriction on apoptotic cell death in pituitary cell s, the present study provides evidence that dietary restriction modula tes somatotropes cell turnover and preserves the cell population for G H secretion during aging.