DISTRIBUTION OF LAMPREY ADRENOCORTICOTROPIN AND MELANOTROPINS IN THE PITUITARY OF THE ADULT SEA LAMPREY, PETROMYZON-MARINUS

Three peptides containing the melanotropin (MSH)-core sequence, YXMXHF RWG, have been isolated recently from the pituitary glands of adult se a lampreys (Petromyzon marinus) and were tentatively assigned as lampr ey adrenocorticotropin (ACTH), MSH-A, and MSHB, respectively. Both MSH s differed significantly from gnathostome MSHs and cannot be assigned as alpha-MSH, beta-MSH, or gamma-MSH. The aim of the present study was to localize these peptides in the lamprey pituitary using antisera ge nerated against synthetic lamprey ACTH(1-16) MSH-A, and MSH-B. ACTH-li ke immunoreactivity was found in most cells of the rostral pars distal is (RPD) and in a few scattered cells of the proximal pars distalis (P PD). MSH-A-like immunoreactivity was found in most cells of the RPD, a few scattered cells of the PPD, and almost all cells of the pars inte rmedia (PI). MSH-B-like immunoreactivity was found only in the PI, whe re almost all cells were stained. Thus, the topographic distributions of ACTH and MSHs in the lamprey pituitary were similar to those in gna thostome vertebrates. (C) 1995 Academic Press, Inc.