The Maximum-Response Control that Makes Every Calcium Experiment Interpretable

August 18, 2026

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Houston Methodist

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Company:

Invitrogen

Product Name:

Ionomycin, Calcium Salt

Catalog Number:

I24222

Every calcium flux experiment we run needs a positive control that produces a maximal, receptor-independent calcium response. Without it, a small response and a badly loaded sample look identical. Ionomycin is also our standard positive control for cell activation assays alongside PMA.

Experimental Design and Results Summary

Application

Cell-Based Assay / Calcium Flux Positive Control

Starting Material

Primary human and mouse immune cells loaded with Fluo-4 and Fura Red, in suspension for flow cytometry or on glass-bottom dishes for imaging, in HEPES-buffered imaging solution.

Tips

Make aqueous working dilutions fresh each session; ionomycin is poorly soluble in water and dilutions do not keep.

Results Summary

Ionomycin does one job and does it completely — as a calcium ionophore it moves calcium across membranes independent of any receptor, so the response is immediate, maximal, and essentially guaranteed if the cells are alive and the dye loaded.

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Summary

The Good

Immediate, maximal, receptor-independent calcium response that makes normalization possible; consistent between lots; negligible cost per experiment at 1 mg.

The Bad

Cytotoxic, so it ends the experiment; poor aqueous solubility means fresh dilutions every session; a degraded stock quietly corrupts your normalization.

The Bottom Line

Not optional if you want your calcium data to mean anything quantitative. Aliquot it once, add it last, and normalize to it.

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