Possible gonadotropin cells in the lamprey pituitary: Colocalization of mammalian LH-like immunoreactivity and glycoconjugate in adult sea lampreys (Petromyzon marinus)

In lampreys, although gonadotropin (GTH) has not yet been isolated from the pituitary gland, the presence of GTH has been strongly suggested. To detec t possible GTH in the sea lamprey (Petromyzon marinus) pituitary, two diffe rent cytochemical probes were tested: One was the use of antibodies to GTHs , and the other was the use of lectin-screening kits for demonstration of g lycoconjugate in hormonal molecules. GTH-like immunoreactivity was found in cells distributed in the ventral half of the proximal pars distalis. These cells were stained intensely by all four lots of anti-ovine LH including L H beta, and were stained moderately or weakly by several other antibodies t o LH-related GTHs, such as human LH beta, hCG beta, amphibian LH, and sturg eon GTH II beta. On the other hand, there were no positive reactions in the sea lamprey pituitary using the antibodies to FSH-related GTHs, thyrotropi n (TSH), or pituitary glycoprotein hormones of teleost origin. Thus, GTH-li ke material in the sea lamprey pituitary seems to be more closely related t o mammalian-like LH, rather than to FSH or TSH, as far as immunocytochemica l determinants. A total of 21 kinds of lectins was tested. Among those, GTH -positive cells were also stained positively by concanavalin A and Vicia vi llosa agglutinin. Thus, the present study demonstrates colocalization of LH -like immunoreactivity and glycoconjugate in cells in the ventral half of t he proximal pars distalis of the sea lamprey pituitary, It is suggested tha t those cells are most likely to be GTH cells in the sea lamprey pituitary. (C) 1999 Academic Press.