Inositol and inositol 1,4,5‐trisphosphate content of Down syndrome fibroblasts exhibiting enhanced inositol uptake

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Abstract
Fibroblasts from individuals with Down syndrome (DS; trisomy 21) exhibit increased inositol uptake. Here we examine the relationship between this increase in uptake and mass levels of free inositol and inositol 1,4,5‐trisphosphate (IP3) in DS fibroblasts. We report that human fibroblasts contain high levels of free inositol which are not significantly affected by the increase in inositol uptake associated with DS. In addition, increased uptake is accompanied by increased efflux of radiolabelled inositol from DS cells. Neither basal nor bradykinin‐stimulated IP3 levels in DS cells differ significantly from normal values. This work highlights the usefulness of the DS cell in uncovering the role of transport across the plasma membrane in cellular inositol homeostasis.