Identification of calcium-activated potassium channels in cultured equine sweat gland epithelial cells.

The research study is about the identification and properties of calcium-activated potassium channels in cultured horse sweat gland cells. This was possible using a patch-clamp recording technique. The researchers established that activity of the channels increases with membrane depolarization and an increase in internal calcium concentration. Moreover, it was found that the potassium channels potentially play a part in the regulation of fluid secretion in sweat glands.

Key Observations of the Research

The researchers made several significant observations in this study:

• The technique used to investigate the properties of K+ channels in the sweat gland cells was the patch-clamp recording approach. This physiological technique allows the study of individual or multiple ion channels in cells.
• A single type of potassium channel was identified. The characteristics of these channels were marked by a slope conductance of 187 pS and a reversal potential of approximately 0 mV. Essentially, this means that these channels are more permeable to potassium ions than to sodium ions.
• The activity of these channels was found to increase with membrane depolarization. This is a process where the cell’s membrane potential becomes less polarized than the resting potential.

The Role of Internal Calcium Concentration and Tetraethylammonium Ions

• An increase in the internal calcium ion concentration resulted in an approximate 60 mV negative shift in the open state probability-voltage curve. This implies that a higher concentration of calcium ions triggers an increase in the likelihood of these channels being open.
• Tetraethylammonium ions (TEA+), when applied externally, resulted in a rapid and irregular blockage of the channel and a reduced unitary current amplitude. This means that TEA+ can influence the operation of the potassium channels.

The Effect of ATP and Other Substances

• The study pointed out that neither glibenclamide (which is an anti-diabetic drug) nor intracellular adenosine 5′-triphosphate (ATP) altered the activity of the potassium channels.
• Contrarily, when ATP was applied externally, it momentarily activated the channel by increasing the open state probability.

Potential Role of the Potassium Channels

• The authors speculate that these channels may not contribute to the resting potassium conductance since their activity was low around the resting membrane potential in intact epithelia.
• Nevertheless, the researchers opine that the potassium channels might have an important role in transepithelial fluid secretion in the sweat gland, potentially playing a part in a regulated manner. The transepithelial fluid secretion is the process of fluid secretion across a layer of cells.