ACTH-related material in the pituitary gland of the chinook salmon ( Oncorhynchus tschawytscha)

Abstract

The distribution and nature of ACTH-related material in the pituitary gland of chinook salmon ( Oncorhynchus tschawytscha) was studied. Pars distalis (PD) and neurointermediate lobe (NIL) extracts were analyzed by gel filtration on BioGel P6 and the resultant fractions assayed for ACTH immunoreactivity (ACTH-IR) using six different antibodies, all of which were specific for ACTH when applied to mammalian samples, and for α-MSH. In the PD a number of distinct peaks of ACTH-IR were observed, which were detected to different degrees by the different ACTH antibodies. Three of the ACTH antibodies produced essentially similar results. The other ACTH antibodies produced results quite distinct from these, and distinct from one another. Thus ACTH-IR is present in the salmon PD in a number of distinct forms, all of which appear to have molecular weights between about 2000 and 5000. No α-MSH was detected in the PD. All of the ACTH antibodies also detected material in the NIL. In general the different antibodies produced similar results. There were fewer peaks of ACTH-IR in the NIL than in the PD. The major one of these, which eluted between the void volume and 1–39 ACTH, was detected by all the antibodies. One of the antibodies also detected a peak of ACTH-IR which eluted close to where α-MSH eluted. All of the ACTH antibodies detected more material in the PD than in the NIL, the ratio being about 3:1 in every case. α-MSH-IR eluted as a minor peak at the void volume, and a major peak in the position of authentic 1–13 α-MSH.