REGULATION OF GFAP EXPRESSION IN GLIAL-LIKE CELLS OF THE RAT PITUITARY INTERMEDIATE LOBE BY LACTATION, SALT-LOADING, AND ADRENALECTOMY

Glial-like cells in rat pituitary intermediate lobe were localized and characterized by immunohistochemistry with antisera against glial fib rillary acidic protein (GFAP) and S-100. Individual GFAP immunoreactiv e (IR) cells possessed several processes that often branched into seco ndary and tertiary processes, terminating with end-feet. The GFAP-immu nopositive cell population was distributed in specific rostrocaudal an d dorsoventral patterns. The distribution and numbers of cells differe d between male and female rats. Examination of altered physiological s tates, e.g., adrenalectomy, lactation, and salt-loading, revealed stat e-specific changes in the appearance and distribution of GFAP-IR cells . Adrenalectomy and lactation increased GFAP-IR glial-like cell number s, whereas salt-loading decreased their numbers and the typical patter n of distribution. By contrast, S-100-expressing cells were evenly dis tributed in male and female rats, and its expression was not affected by the experimental conditions. Double-label immunocytochemistry indic ated that GFAP-IR cells are a subpopulation of S-100-IR cells. These r esults suggest that cells normally expressing only S-100 may be induce d to express GFAP under altered physiologic conditions. (C) 1995 Wiley -Liss, Inc.