title: Structure and steroidogenesis of the placenta in the Antarctic minke whale (Balaenoptera bonaerensis).
abstract: There are few reports describing the structure and function of the whale placenta with the advance of pregnancy. In this study, therefore, the placenta and nonpregnant uterus of the Antarctic minke whale were observed morphologically and immunohistochemically. Placentas and nonpregnant uteri were collected from the 15th, 16th and 18th Japanese Whale Research Programme with Special Permit in the Antarctic (JARPA) and 1st JARPA II organized by the Institute of Cetacean Research in Tokyo, Japan. In the macro- and microscopic observations, the placenta of the Antarctic minke whale was a diffuse and epitheliochorial placenta. The chorion was interdigitated to the endometrium by primary, secondary and tertiary villi, which contained no specialized trophoblast cells such as binucleate cells, and the interdigitation became complicated with the progress of gestation. Furthermore, fetal and maternal blood vessels indented deeply into the trophoblast cells and endometrial epithelium respectively with fetal growth. The minke whale placenta showed a fold-like shape as opposed to a finger-like shape. In both nonpregnant and pregnant uteri, many uterine glands were distributed. The uterine glands in the superficial layer of the pregnant endometrium had a wide lumen and large epithelial cells as compared with those in the deep layer. On the other hand, in the nonpregnant endometrium, the uterine glands had a narrower lumen and smaller epithelial cells than in the pregnant endometrium. In immunohistochemical detection, immunoreactivity for P450scc was detected in most trophoblast cells, but not in nonpregnant uteri, suggesting that trophoblast epithelial cells synthesized and secreted the sex steroid hormones and/or their precursors to maintain the pregnancy in the Antarctic minke whale.
authors.affiliation: Laboratory of Veterinary Anatomy, Department of Basic Veterinary Medicine, Obihiro University of Agriculture and Veterinary Medicine, Hokkaido 080-8555, Japan. sasakim@obihiro.ac.jp
authors.forename: Motoki
authors.initials: M
authors.lastname: Sasaki
authors.forename: Yoko
authors.initials: Y
authors.lastname: Amano
authors.forename: Daisuke
authors.initials: D
authors.lastname: Hayakawa
authors.forename: Toshio
authors.initials: T
authors.lastname: Tsubota
authors.forename: Hajime
authors.initials: H
authors.lastname: Ishikawa
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Mogoe
authors.forename: Seiji
authors.initials: S
authors.lastname: Ohsumi
authors.forename: Masafumi
authors.initials: M
authors.lastname: Tetsuka
authors.forename: Akio
authors.initials: A
authors.lastname: Miyamoto
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Fukui
authors.forename: Teguh
authors.initials: T
authors.lastname: Budipitojo
authors.forename: Nobuo
authors.initials: N
authors.lastname: Kitamura
mesh_terms: D000818:Animals; D005260:Female; D012739:Gonadal Steroid Hormones / Q000096:biosynthesis*; D050636:Minke Whale / Q000033:anatomy & histology* / Q000378:metabolism; D010920:Placenta / Q000033:anatomy & histology* / Q000378:metabolism; D010929:Placentation / Q000502:physiology*; D011247:Pregnancy; D014327:Trophoblasts / Q000378:metabolism
chemical_list: D012739:Gonadal Steroid Hormones