title: Angiogenesis in the intermediate lobe of the pituitary gland alters its structure and function.
abstract: The pars distalis (PD) and the pars intermedia (PI) have the same embryonic origin, but their morphological and functional characteristics diverge during development. The PD is highly vascularized, whereas the highly innervated PI is essentially non-vascularized. Based on our previous finding that vascular endothelial growth factor-A (VEGF-A) is involved in vascularization of the rat PD, attempt was made to generate transgenic Xenopus expressing VEGF-A specifically in the melanotrope cells of the PI as a model system for studying the significance of vascularization or avascularization for the functional differentiation of the pituitary. The PI of the transgenic frogs, examined after metamorphosis, were distinctly vascularized but poorly innervated. The experimentally induced vascularization in the PI resulted in a marked increase in tissue volume and a decrease in the expression of both alpha-melanophore-stimulating hormone (α-MSH) and prohormone convertase 2, a cleavage enzyme essential for generating α-MSH. The transgenic animals had low plasma α-MSH concentrations and displayed incomplete adaptation to a black background. To our knowledge, this is the first report indicating that experimentally induced angiogenesis in the PI may bring about functional as well as structural alterations in this tissue.
authors: Integrated Bioscience Section, Graduate School of Science and Technology, Shizuoka University, Shizuoka 422-8529, Japan. sbstana@ipc.shizuoka.ac.jp
authors: Shigeyasu
authors: S
authors: Tanaka
authors: Takashi
authors: T
authors: Nakakura
authors: Eric J R
authors: EJ
authors: Jansen
authors: Keisuke
authors: K
authors: Unno
authors: Reiko
authors: R
authors: Okada
authors: Masakazu
authors: M
authors: Suzuki
authors: Gerard J M
authors: GJ
authors: Martens
authors: Sakae
authors: S
authors: Kikuyama
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology; D000818:Animals; D030801:Animals, Genetically Modified; D005260:Female; D008297:Male; D018919:Neovascularization, Physiologic; D010902:Pituitary Gland / Q000098:blood supply / Q000166:cytology; D052716:Pituitary Gland, Intermediate / Q000098:blood supply / Q000166:cytology / Q000502:physiology*; D045706:Proprotein Convertase 2 / Q000378:metabolism; D042461:Vascular Endothelial Growth Factor A / Q000502:physiology*; D014982:Xenopus laevis; D000521:alpha-MSH / Q000096:biosynthesis / Q000097:blood
chemical_list: D042461:Vascular Endothelial Growth Factor A; D000521:alpha-MSH; D045706:Proprotein Convertase 2