Tetraethylammonium-induced calcium concentration changes in skin fibroblasts from patients with Alzheimer disease.

Potassium (K+) channel dysfunction in fibroblasts was recently proposed as a potential diagnostic marker for Alzheimer disease (AD). We utilized a microspectrofluorometric method with Fura-2AM to measure intracellular free calcium ([Ca2+]i) following depolarization with the K+ channel blocker tetraethylammonium (TEA) in seven AD and seven control fibroblast cultures. Contrary to our expectation, 43% of the AD and 36% of the control fibroblast plated coverglasses responded with an increase in [Ca2+]i on addition of 100 mM TEA. The data suggest that the TEA-elicited [Ca2+]i response is not a useful AD screening test.