Preparation of Enriched Populations of Cortic Rostra1 Pars Distatis

A mammalian isolated adrenal cell system was validated as a bioassay for goldfish ACTH; the log dose-response curve for the goldfish hormone is parallel to that for synthetic mammalian ACTHI-,,, and the two ACTHs induce the same maximum rate of corticosterone production. Using this assay, it was observed that (1) there is a marked and consistent bipbasic change in pituitary ACTH content as related to the length of time the fish are heid in laboratory aquaria, and (2) the absolute and relative (to tissue wt) ACTH content of the rostra1 pars distalis is considerably greater than that of the proximal portion of the gland. Using a trypsin technique, isolated pituitary cells were prepared from both (rostra1 and proximal) portions of the gland; bioassay data indicate that cell suspensions prepared from the rostral pars distalis are enriched with respect to corticotrophs. The implications of these findings with regard to formulating an advantageous in vitro system for studying ACM secretion are discussed.