GIE filterability is dependent on cAMP concentration.

Abstract

<p><b>A.</b> cAMP concentration drops in mature GIE. The total intracellular cAMP concentration was measured in stage III and V GIE using a competitive immunoassay for the quantitative determination of cAMP. GIE were harvested by magnetic isolation and aliquots of 6.10⁶ cells were assayed in duplicate wells. The assay was carried out three times. Error bars denote the standard error of the mean. **Highly significant difference compared to stage III GIE (<i>P <</i> 0.01). <b>B</b>. Western-blot analysis of PKA-R expression in MACS-purified stage III and stage V GIE (5.10e6 parasites/lane). Immunoblots were probed with rabbit polyclonal antibodies directed against <i>Pf</i>PKA-R and with a mAb directed against <i>Pf</i>HSP70 to normalize expression. Quantity One (BioRad) analysis shows that <i>Pf</i>PKA-R levels were not significantly different between stage III and stage V. <b>C</b>. Retention rates in microsphilters of stage III GIE (dark grey), stage V GIE (light grey) and uninfected red blood cells (uRBC, black) pre-incubated 15 min at 37°C with different concentrations of 8Br-cAMP. Error bars denote the standard error of the mean. Outliers are shown as open circles. **Highly significant differences in retention rates compared to control without 8Br-cAMP (<i>P <</i> 0.01); ns: non-significant differences in retention rates compared to control; n: number of experiments.</p