Time course of [Pyr1]apelin-13-induced HA-mAPJ localization and expression levels. HA-mAPJ-HEK293 cells were incubated in the presence or absence of [Pyr1]apelin-13 (100 nM) for 0–6 h. Cells were fixed, stained and imaged for determination of either (A) cell surface or (B) whole cell HA-mAPJ intensity using anti-HA antibody. The value determined with no primary antibody present was designated as background and was subtracted from raw data to give HA-mAPJ intensity in arbitrary fluorescence units (AFU) and then normalized to a percentage of vehicle control. Cell surface and whole cell AFU values were used to determine the PCSE (C). Data shown are mean ± SEM, of at least three separate experiments, each with triplicate wells and triplicate fields within wells. * = p < 0.05 and ** = p < 0.01, comparing stimulations to basal conditions, analysed by one-way ANOVA and Dunnett's multiple comparison post hoc tests.