Bioassay studies of rostral and caudal halves of the pars distalis of Rana pipiens for adrenocorticotropin and gonadotropin

Abstract

The ratio of potency for corticotropin (ACTH) between the rostral and caudal half-lobes of the pars distalis of Rana pipiens was determined using an assay in dexamethasone suppressed rats and International Working Standard Corticotrophin (1962). On the basis of assays of single lobes, in the rostral half there was 3.2 times more ACTH than in the caudal half. When extracts from pooled half-lobes were assayed the potency ratio for ACTH with 95% fiducial limits was rostral: caudal 4.2 (3.0–6.1):1. Because in the rostral half-lobe there are 7 times as many basophilic purple cells as in the caudal half-lobe and no other cell type is concentrated in the rostral lobe, we assign ACTH production to these cells. The distribution of gonadotropic activity between the rostral and caudal halves was studied using an assay in hypophysectomized immature male rats and equine luteinizing hormone (LH). There was 1.4 times more gonadotropic activity in the caudal half-lobes than the rostral lobes, and we provisionally assign gonadotropin production in the frog pituitary to the cell type staining with acid fuchsin or aniline blue cells type 1 or type 2.