title: Hepatic confinement of newly produced erythrocytes caused by low-temperature exposure in Xenopus laevis.
abstract: Diminished erythrocyte count and erythropoiesis have been reported during hypothermia in some ectothermic animals. In this study, the African clawed frog, Xenopus laevis, was used to investigate the cause of hypothermia-induced anemia. We developed a new model of hypothermia at 5°C and monitored blood cell count and erythropoiesis on several days. Erythrocyte count declined by 30% on the first day following cold exposure (5°C) and mRNA expression of hemeoxygenase-1 was enhanced 10-fold; accumulation of iron as a result of heme degradation was observed in the liver. One day after low-temperature exposure, erythropoietin mRNA expression was elevated in the liver and lung compared with that at normal temperature (22°C) by qRT-PCR analysis. Examination of liver sections (i.e. the erythropoietic organ) showed an increase in o-dianisidine-positive erythrocytes in the hepatic sinusoid 5 days after the onset of low-temperature exposure compared with normal liver. Peripheral erythrocyte count remained low, indicating that newly produced erythrocytes did not migrate from the liver to the circulation during hypothermia. In conclusion, this study reveals hypothermic anemia as being associated with hepatic erythrocyte destruction; prolonged anemia during low-temperature exposure is concomitant with newly produced erythrocytes being confined to the liver and may lead to new insights into vertebrate hematopoiesis.
authors.affiliation: Department of Biology, School of Education, Waseda University, 2-2 Wakamatsu, Shinjuku, Tokyo, 162-8480,  Japan.
authors.forename: Shun
authors.initials: S
authors.lastname: Maekawa
authors.forename: Hitomi
authors.initials: H
authors.lastname: Iemura
authors.forename: Yuko
authors.initials: Y
authors.lastname: Kuramochi
authors.forename: Nami
authors.initials: N
authors.lastname: Nogawa-Kosaka
authors.forename: Hironori
authors.initials: H
authors.lastname: Nishikawa
authors.forename: Takehito
authors.initials: T
authors.lastname: Okui
authors.forename: Youichi
authors.initials: Y
authors.lastname: Aizawa
authors.forename: Takashi
authors.initials: T
authors.lastname: Kato
mesh_terms: D000740:Anemia / Q000097:blood / Q000473:pathology; D000818:Animals; D001973:Bromodeoxyuridine / Q000378:metabolism; D049109:Cell Proliferation; D003080:Cold Temperature; D004781:Environmental Exposure; D004906:Erythrocyte Count; D004912:Erythrocytes / Q000378:metabolism* / Q000473:pathology; D004920:Erythropoiesis; D008099:Liver / Q000378:metabolism* / Q000473:pathology*; D008297:Male; D008954:Models, Biological; D060888:Real-Time Polymerase Chain Reaction; D014982:Xenopus laevis / Q000502:physiology*
chemical_list: D001973:Bromodeoxyuridine