Hepatic confinement of newly produced erythrocytes caused by low-temperature exposure inXenopus laevis

Abstract

SUMMARYDiminished 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.

Enhanced erythropoiesis in mice exposed to low environmental temperature

“…Several studies have demonstrated that anemia can be induced by low temperature exposure in ectothermic animals. We also used Xenopus laevis in a model of hypothermia and investigated the causes of anemia induced by low temperature exposure (Maekawa et al, 2012). We found that hypothermic anemia is associated with hepatic erythrocyte destruction and that prolonged anemia during low temperature exposure is concomitant with newly produced erythrocytes being confined to the liver in Xenopus laevis.…”

“…We also determined the anemia induced by low temperature exposure in the African clawed frog, Xenopus laevis (Maekawa et al, 2012). We observed enhanced hepatic destruction of erythrocytes immediately after exposure to low temperature.…”

Water Temperature Affects Susceptibility to Ranavirus

“…Thus, FV3-infiltrated immune cell vectors would be relatively confined to animal peripheries, resulting in lower kidney and liver FV3 loads and greater animal survival, as we observed. Decreased blood circulation, which is known to occur in ectothermic vertebrates at lower temperatures (Engelsma et al 2003;Maekawa et al 2012), may also have contributed to reduced phagocyte, and hence FV3 dissemination.…”

Cellular characterization of thrombocytes in Xenopus laevis with specific monoclonal antibodies

“…The EPOR-expressing erythroid progenitors were observed to localize on the inner wall of the hepatic sinusoids [17]. In addition, we found that X. laevis exposed to low environmental temperature developed acute pancytopenia, including thrombocytopenia [18] with modulation of the hepatic proteome [19]. Thus, X. laevis is a valuable animal model for analysis of hematopoiesis and environmental response.…”

“…In fact, we previously developed a unique pancytopenic model of X. laevis by exposure to reduced temperatures. In that model, thrombocyte count gradually decreased at 5 C to approximately 60% of the original values [18,19]. However, it was difficult to analyze thrombocyte metabolism owing to lack of specific methods to trace thrombocytes.…”