Occurrence of immunoreactive Activin/Inhibin beta(B) in thyrotropes and gonadotropes in the bullfrog pituitary: possible Paracrine/Autocrine effects of activin B on gonadotropin secretion.
Occurrence of immunoreactive activin/inhibin beta(B) in the bullfrog (Rana catesbeiana) pituitary was investigated immunocytochemically by use of antibody against Xenopus activin/inhibin beta(B) subunit. Thyrotropes were demonstrated to contain activin/inhibin beta(B)-immunoreactive substances. Moreover, immunoelectron microscopy revealed that in the secretory granules of thyrotropes and, to a lesser extent, in those of gonadotropes, activin/inhibin beta(B)-immunoreactive substances were present. Based on this observation, we investigated the effect of activin B on the release of gonadotropins from dispersed anterior pituitary cells of the bullfrog. Activin B stimulated the release of not only follicle-stimulating hormone (FSH) but also luteinizing hormone (LH) dose dependently. Under the culture conditions used in this experiment, inhibin B, as well as follistatin, did not affect the basal levels of LH and FSH, but they suppressed the activin-induced release of these hormones. This is the first study on the effect of activin on pituitary hormone secretion in lower tetrapods.
Uchiyama
H
H
Department of Environmental Science, Yokohama City University, 22-2 Seto, Kanazawa-ku, Yokohama, 236-0027, Japan. hideho@yokohama-cu.ac.jp
Koda
A
A
Komazaki
S
S
Oyama
M
M
Kikuyama
S
S
D028341:Activins; D000818:Animals; D019898:Autocrine Communication / Q000502:physiology*; D038681:Follistatin; D006023:Glycoproteins / Q000378:metabolism; D006062:Gonadotropins / Q000378:metabolism*; D006133:Growth Substances / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D016253:Microscopy, Immunoelectron; D009842:Oligopeptides; D019899:Paracrine Communication / Q000502:physiology*; D010455:Peptides / Q000378:metabolism*; D010903:Pituitary Gland, Anterior / Q000033:anatomy & histology / Q000166:cytology / Q000378:metabolism*; D011892:Rana catesbeiana; D011994:Recombinant Proteins / Q000494:pharmacology; D013972:Thyrotropin / Q000378:metabolism*; D014981:Xenopus / Q000378:metabolism
D038681:Follistatin; D006023:Glycoproteins; D006062:Gonadotropins; D006133:Growth Substances; D009842:Oligopeptides; D010455:Peptides; D011994:Recombinant Proteins; C044147:activin B; D028341:Activins; C048617:myelopeptides; D013972:Thyrotropin