= Pancreatic IP3 store fractionation experiment
{c}
A 1984 primary experiment localized <IP3>-evoked release using <pancreatic acinar cells> isolated from rat <pancreas> with <collagenase>. A homogenized preparation was separated by <differential centrifugation>, then by a <sucrose> step <density gradient> or precipitation with <magnesium> chloride. The readout was <IP3>-induced <calcium> release per mass of <protein> across fractions. Release tracked two <endoplasmic reticulum> markers, <RNA> content and an <enzyme> activity, across several separation methods. Marker activities for <mitochondria> and the <cell membrane> supplied contrasting comparisons: release correlated negatively with them.<Effect of inositol-1,4,5-trisphosphate on isolated subcellular fractions of rat pancreas by H. Streb and others>[Streb, Bayerdörffer, Haase, Irvine and Schulz, Effect of inositol-1,4,5-trisphosphate on isolated subcellular fractions of rat pancreas (1984), abstract: preparation, separation methods, protein-normalized release and marker correlations]{ref}
Agreement across distinct fractionations supports an <endoplasmic reticulum>-associated source in this preparation. “Nonmitochondrial” alone only excludes a candidate; positive compartment markers add localization evidence. Marker comparisons control the localization inference, rather than replacing a no-<IP3> release comparison. Fractionation may mix or damage compartments, and correlation does not itself identify the <IP3 receptor> <protein>. This <calcium> release readout also does not directly measure secretion or establish identical responses in every <biological cell>.
Back to article page
