Microtubules (MTs) are self-assembled proteinaceous filaments with nanometer scale diameters and micrometer scale lengths. Through conductivity measurements in microchannels we shed some light on electrical properties of microtubules. Measuring electrical resistance we were able to detect the dynamic disassembly of MTs and determine an upper limit for the electrical conductivity of MT. The measurements yielded the value of 90 Omega(-1) m(-1) as the upper limit for the conductivity of MTs, which is in the order of conductivity observed in inorganic intrinsic semiconductors.