Evidence That the Gonadotrophs Are the Likely Site of Production of Angiotensin II in the Anterior Pituitary of the Rat*

To determine whether the angiotensin II-like immunoreactivity (AII-IR) previously reported in rat gonadotrophs is generated locally, we stained for AII-IR in neonatal rat pituitary explants and dispersed adult pituitary cells maintained in serum-free medium. In both preparations, AII-IR was found in cells with the morphological characteristics of gonadotrophs. In the anterior pituitaries of adult male rats, AII-IR and LH beta immunoreactivity were found by electron microscopy to be located in the same secretory granules. Pituitary tissue was also extracted, and the AII content was measured by RIA. The gland contained 300 times more AII than could be accounted for by the extracellular fluid in the gland. On HPLC, the pituitary AII-IR comigrated with synthetic Ile5-AII. Thus, it appears that the AII-IR in rat pituitary gonadotrophs is AII and that it is likely to be produced within these cells.