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The heterogeneity of ion channels in chromaffin granule membranes


Chromaffin granules are involved in catecholamine synthesis and traffic in the adrenal glands. The transporting membrane proteins of chromaffin granules play an important role in the ion homeostasis of these organelles. In this study, we characterized components of the electrogenic 86Rb+ flux observed in isolated chromaffin granules. In order to study single channel activity, chromaffin granules from the bovine adrenal medulla were incorporated into planar lipid bilayers. Four types of cationic channel were found, each with a different conductance. The unitary conductances of the potassium channels are 360 ± 10 pS, 220 ± 8 pS, 152 ± 8 pS and 13 ± 3 pS in a gradient of 450/150 mM KCl, pH 7.0. A multiconductance potassium channel with a conductivity of 110 ± 8 pS and 31 ± 4 pS was also found. With the exception of the 13 pS conductance channel, all are activated by depolarizing voltages. One type of chloride channel was also found. It has a unitary conductance of about 250 pS in a gradient of 500/150 mM KCl, pH 7.0.



black lipid membrane technique


single-channel current amplitude


large conductance potassium channel

Po :




Urev :

reversal potential


ion conductance

τo :

mean open lifetime

τo :

mean closed lifetime


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Correspondence to Krzysztof Dołowy.

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Hordejuk, R., Szewczyk, A. & Dołowy, K. The heterogeneity of ion channels in chromaffin granule membranes. Cell Mol Biol Lett 11, 312–325 (2006).

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Key words

  • Chromaffin granule
  • Intracellular channel
  • Potassium channel
  • Chloride channel
  • Black lipid membrane