AJP - Cell Physiology, Vol 267, Issue 2 C435-C442, Copyright © 1994 by American Physiological Society

ARTICLES

Carbon monoxide stimulates a potassium-selective current in rabbit corneal epithelial cells

A. Rich, G. Farrugia and J. L. Rae
Department of Physiology and Biophysics, Mayo Foundation, Rochester, Minnesota 55905.

The effects of CO on ion currents in freshly dispersed rabbit corneal epithelial cells were assessed using the perforated patch whole cell voltage-clamp technique. Bath perfusion with 1% CO resulted in a 84 +/- 18% (mean +/- SE, n = 14) increase in potassium current (IK) and a membrane hyperpolarization from -42 +/- 4 to -51 +/- 4 mV. The CO-stimulated current reversed at -64 +/- 7 mV [reverse potential (EK) = -87 mV]. The stimulated current was blocked by 1 mM quinidine or 1 mM diltiazem, agents that inhibit IK in rabbit corneal epithelial cells. Single potassium-channel currents measured in the cell-attached configuration showed that exogenous CO increased the steady-state open probability from 0.003 to 0.156 at a holding potential of -40 mV. CO did not affect open probability in excised patches. The single-channel conductance measured from -40 to +40 mV was unaffected. Intracellular guanosine 3',5'-cyclic monophosphate (cGMP) concentration measured with radioimmunoassay techniques was found to increase from 0.41 +/- 0.24 to 0.55 +/- 0.27 pmol/10(6) cells after the addition of 1% CO (P < 0.05). The data show that bath perfusion with exogenous CO activates IK and hyperpolarizes the resting membrane potential; the data also suggest that CO modulates intracellular cGMP concentration.

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