Placental Uric Acid Transport System: Glucose Transporter 9 (SLC2A9)

Placental Uric Acid Transport System: Glucose Transporter 9 (SLC2A9). INTRODUCTION: Pre-eclampsia, a pregnancy-specific disease, contributes substantially to perinatal morbidity and mortality of both the mother and her child. Pre-eclampsia is often associated with high maternal urate serum levels, which in turn has been shown to play a role in the pathogenesis of this disease. The aim of this study was to investigate the glucose transporter GLUT9-mediated placental uric acid transport system. METHODS: In this study western blot, immunofluorescence techniques as well as a transepithelial transport (Transwell) model were used to assess GLUT9 protein expression and, respectively, uric acid transport activity. Electrophysiological techniques and transmission electron microscopy (TEM) were used to characterize the properties and the structure of GLUT9. RESULTS: Uric acid is transported across a BeWo choriocarcinoma cell monolayer with 530 pmol/min. We could successfully overexpress and for the first time purify the GLUT9b isoform using the Xenopus laevis oocytes expression system. Chloride seems to modulate the urate transport system. TEM revealed that GLUT9b isoform is present as monomer and dimmer in the Xenopus laevis overexpression model. A class average of all the particles allowed us to develop a first model of human GLUT9b structure, which was derived from the published crystal structure of the bacterial homologue of GLUT1-4. CONCLUSIONS: In vitro the “materno-fetal” transport of uric acid is slow indicating that in vivo the fetus might be protected from short-term fluctuations of maternal urate serum levels. The low-resolution structure obtained from TEM validates the proposed homology model regarding the structure of human GLUT9b. In ongoing studies this model is used to perform virtual screening to identify novel modulators of the urate transport system enabling the development of novel therapies in pregnancy complications.

Respiration rates and electron transport system activities of copepod species obtained during Maria S. Merian cruise MSM17/3

Respiration rates and electron transport system (ETS) activities were measured in dominant copepod species from the northern Benguela upwelling system in January-February 2011 to assess the accuracy of the ETS assay in predicting in vivo respiration rates. Individual respiration rates varied from 0.06 to 1.60 µL O2/h/ind, while ETS activities converted to oxygen consumption ranged from 0.14 to 4.46 µL O2/h/ind. ETS activities were significantly correlated with respiration rates (r**2 = 0.79, p = 0.0001). R:ETS ratios were lowest in slow-moving Eucalanidae (0.11) and highest in diapausing Calanoides carinatus copepodids CV (0.76) while fast-moving copepods showed intermediate R:ETS (0.23-0.37). 82% of the variance of respiration rates could be explained by differences in dry mass, temperature and the activity level of different copepod species. Three regression equations were derived to calculate respiration rates for diapausing, slow- and fast-moving copepods, respectively, based on parameters such as body mass and temperature. Thus, knowledge about the activity level and behavioral characteristics of copepod species can significantly increase the predictive accuracy of metabolic models, which will help to better understand and quantify the impact of copepods on nutrient and carbon fluxes in marine ecosystems.