Ba2+ release from soda glass modifies single maxi K+ channel activity in patch clamp experiments

Area of Science:

• Biophysics
• Cell Physiology
• Materials Science

Background:

• Patch pipettes are crucial tools in ion channel research.
• The type of glass used for patch pipettes can influence experimental results.
• Previous studies suggest glass components may affect ion channel activity.

Purpose of the Study:

• To investigate the effect of different glass types on maxi K+ channel gating.
• To identify components released from glass pipettes that may alter ion channel function.
• To determine if barium ions released from glass cause channel block.

Main Methods:

• Patch-clamp electrophysiology on Necturus gallbladder epithelium maxi K+ channels.
• Preparation of Ringer's solution preincubated with borosilicate glass (BG) and blue tip hematocrit glass (SG).
• Mass spectrometry analysis of ions released from SG.

Main Results:

• Maxi K+ channel gating properties differed based on BG or SG pipette use.
• Ringer's solution preincubated with SG, but not BG, blocked inside-out maxi K+ channels.
• Mass spectrometry confirmed Ba2+ release from SG, consistent with observed channel block.
• SG also released O2-, Na+, Ca2+, and Mg2+ to micromolar concentrations.

Conclusions:

• Blue tip hematocrit glass releases barium ions that cause a voltage-dependent, cytosolic-side specific block of maxi K+ channels.
• Borosilicate glass does not release significant amounts of barium or affect channel block.
• Researchers must screen for glass-released substances to ensure accurate patch-clamp results.