ENDOHM CHAMBERS

Endohm’s symmetrically opposing circular disc electrodes, situated above and beneath the membrane, allow a more uniform current density to flow across the membrane than with electrodes. The background resistance of a blank insert is reduced from 150Ω (when using WPI’s hand-held electrodes) to less than 5 Ω. With Endohm’s fixed electrode geometry, variation of readings on a given sample is reduced from 10-30 Ω with electrodes to 1-2 Ω. Compared with other resistance measurement methods, Endohm with EVOM™ Manual offers a much more convenient and economic solution to “leaky tissue” measurement. Because of the uniform density of the AC square wave current from EVOM™ Manual, errors owing to electrode polarization or membrane capacitance are largely negated. Endohm together with EVOM™ Manual offers the most accurate and economical endothelial ohmmeter now available. To date, cups from Corning, Millipore, Nunc, Greiner, and BD Falcon have been tested. Endohm chambers may be sterilized with EtO, alcohol, or a bactericide; not autoclavable.

Note that EndOhm chambers may not be suited for continuous measurements for extended periods of time since the EndOhm chamber electrodess are silver/silver chloride-based and may show potential cytotoxic effects during long term exposure.

Note that EndOhm chambers may not be suited for continuous measurements for extended periods of time since the EndOhm chamber electrodess are silver/silver chloride-based and may show potential cytotoxic effects during long term exposure.Resistance values obtained with the Endohm are consistent with those obtained using a well-designed Ussing Chamber. Options include:

• EVM-EL-03-01-01 (ENDOHM-6G) Chamber for 6 mm culture cup, 15.8 mm ID (24 wells per plate)
• EVM-EL-03-01-02 (ENDOHM-12G) Chamber for 12 mm culture cup, 23.2 mm ID (12 wells per plate)
• EVM-EL-03-01-03 (ENDOHM-24G-SNAP) Chamber for 24 mm and COSTAR Snapwell™ culture cup, 37.3 mm ID(6 wells per plate)

The chamber and the cap each contain a pair of concentric electrodes: a voltage-sensing silver/silver chloride pellet in the center plus an annular current electrode. Current flows between these symmetrically opposing circular disc electrodes. This design provides several advantages:

• Current density across the membrane is more uniform with Endohm’s circular disc current electrodes than with the STX4 electrodes.
• Most importantly, with Endohm’s fixed electrode geometry, variation between successive resistance measurements of the same sample is only 1–2Ω.