Serum of Isaacs' syndrome suppresses potassium channels in PC-12 cell lines

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Abstract
Blockage of K+ channels in nerve terminals by immunoglobulin is the speculated pathomechanism of Isaacs' syndrom. Using patch‐clamp technique (whole‐cell clamp), we investigated the effects on K+ current of serum taken from 2 patients with Isaacs' syndrom employing the clonal cell line PC‐12. The addition of a patient's serum to the perfusion solution had little effect on the K+ current of P‐12 cells. In contrast, K+ current was reduced by 25–80% when cells were cultured for 3–6 days with 2% serum as compared to control serum values. Supperession of the K+ current appears to develop gradually over the period of culture. Our results suggest that the pathomechanism of Isaacs' syndrome is caused by K+ channel suppression via a humoral factor(s) in the serum, which subsequently induces nerve hyperexcitability. © 1996 John Wiley & Sons, Inc.