A reduced functioning of lymphocytes has been reported in a number of pain conditions, such as migraine, cluster headaches and FMS (Galeotti et al., 2001). Potassium (K⁺) channels play a critical role in the functioning and proliferation of lymphocytes. The aim of this study was to investigate, using a Rb⁺ efflux assay, the activity of the K⁺channels in lymphocytes of patients with FMS.

Lymphocytes were isolated from blood, from patients with FMS (n=5) or healthy volunteers (control, n=14), using density-gradient centrifugation. A non-radioactive rubidium efflux assay was used to functionally analyse K⁺channel activity (Terstappen, 1999). The isolated lymphocytes were incubated in 2ml Rb⁺-PSS (Rb⁺ containing physiological salt solution mM: NaCl 118, RbCl 5.8, CaCl₂ 2.5, MgSO₄ 1.2, glucose 11, NaHCO₃ 25, NaH₂PO₄ 1.2) for 18 hrs at 37°C. The cells were washed and resuspended in K⁺-PSS (mM: NaCl 0-118, KCl 4.6-120, CaCl₂ 2.5, MgSO₄ 1.2, glucose 11, NaHCO₃ 25, KH₂PO₄ 1.2) as six aliquots. When the [KCl] was increased above 4.6mM the [NaCl] was decreased from 118mM.K⁺channel modulators were included in the K⁺-PSS. After 10 min incubation the supernatant was removed and collected. Cell lysates were collected by the addition of 2ml Triton X-100 (1%). Rb⁺ content of the supernatant and cell lysate were determined by flame atomic absorption spectroscopy and Rb⁺ efflux (%) was calculated. Data is presented as mean values (±s.e.m.).

Increasing the [KCl] in the supernatant augmented the Rb⁺ efflux (%) with responses in lymphocytes from control and FMS samples not being significantly different (Table 1).

Table 1. Rb⁺ efflux (%) in response to increasing extracellular [KCl].

The Rb⁺ efflux (%) from lymphocytes of FMS patients was different from that of control subjects following exposure to margatoxin (MgTx 10nM) or margatoxin (MgTx 10nM) plus charybdotoxin (ChTx 100nM) when incubated with K⁺ PSS containing 4.6 or 80mM KCl (Table 2). Data for 80mM KCl were corrected for baseline variations by subtraction of the value obtained with 4.6mM KCl.

Table 2. Effects of K⁺channel blockers on Rb⁺ efflux (%).

^aP<0.1, ^bP<0.05 Control vs. FMS (Student’s Unpaired T-test)

In conclusion, although the lymphocytes from FMS patients and healthy volunteers responded similarly to KCl stimulation, responses in the presence of the K⁺channel blockers margatoxin and charybdotoxin differed. These findings support the suggestion that altered K⁺channel function may be associated with FMS (Lawson, 2001).

Galeotti N et al. (2001) Cephalagia 21: 38-45
Lawson K (2001) Myalgies Intl 2: 25-30
Terstappen GC (1999) Anal Biochem 272: 149-155