SYNAPTOPHYSIN IMMUNOREACTIVITY IN THE AGING RAT PITUITARY-GLAND

The density of synaptophysin (SN)-immunoreactivity (IR) was examined i n pituitary glands of aging male Sprague-Dawley rats. SN-IR was observ ed as dense dots among endocrine cells of the intermediate lobe, while the neural lobe contained numerous, highly dense immunopositive regio ns. Some anterior lobe secretory cells contained SN-IR within the cyto plasm, suggestive of the presence of the protein in secretory granules , but no dot-like staining was observed between endocrine cells of tha t region. A quantitative analysis of the dot-like SN-immunostaining wi thin the intermediate lobe found that tissue from groups of rats aged 13 months, or 15-17 months, contained significantly fewer SN-immunopos itive areas than did tissues from 8-month-old animals. Diminished SN i mmunostaining is suggestive of reduced numbers of synapses in the inte rmediate lobe, which may lead to alterations in regulation of pituitar y hormone secretion from endocrine cells in the older animals. (C) 199 7 Elsevier Science Inc.