ELF magnetic fields induce internalization of gap junction protein connexin 43 in Chinese hamster lung cells.

We have previously demonstrated that exposure of Chinese hamster lung (CHL) cells to 50 Hz magnetic fields (MFs) and/or 12-O-tetradecanoylphorbol-3-acetate (TPA)-inhibited gap junctional intercellular communication (GJIC). To explore and compare the mechanisms of GJIC inhibition induced by extremely low frequency (ELF) MF and TPA, the number and localization of connexin 43 (C x 43) were studied. The localization of C x 43 was determined with indirect immunofluorescence histochemical analysis and detected by confocal microscopy after exposing CHL cells to 50 Hz sinusoidal magnetic field at 0.8 mT for 24 h without or with TPA (5 ng/ml) for the last 1 h. The C x 43 levels in nuclei and in cytoplasm were examined by Western blotting analysis. The results showed that the cells exposed to MF and/or TPA displayed individual plaques at regions of intercellular contact, which were fewer than the normal cells in number, while the number of C x 43 in cytoplasm increased and congregated near the nuclei. Western blot analysis further demonstrated the quantity of changes in location of Cx43. These results suggest that reduction of C x 43 at regions of intercellular contact may be one of the mechanisms of GJIC inhibition induced by ELF MF.

[Relative bioavailability of effervescent tablet of potassium chloride in healthy volunteers].

AIM: To probe the approach by which the pharmacokinetics and relative bioavailability of endogenous medicinal substances can be studied. METHODS: A randomized three-crossover study was performed in 18 healthy male volunteers. In two of the three study periods, a single 2 g dose of either effervescent tablet or common tablet of potassium chloride was administered; whereas in one of three periods no drug treatment was given to allow the nondrug-related (endogenous) potassium in urine to be determined. In each period the urine samples were collected at the following intervals: 0-2, 2-4, 4-6, 6-8, 8-10, 10-12, 12-24, 24-48 h after dose. Urine potassium was determined and the cumulative urine potassium-time data were fitted to a one-compartment model with first-order absorption. Bioavailability was represented by cumulative amount of potassium excreted in urine during 48 hours after drug administration and the bioequivalence of the two formulations was evaluated by analysis of variance and two one-sided t-test. RESULTS: The pharmacokinetic parameters were as follows: effervescent tablet T1/2 ke = (6 +/- 5) h, T1/2 ka = (0.08 +/- 0.08) h, ku = (0.09 +/- 0.04) h-1, Xmax/f = (18 +/- 8) mmol; common tablet T1/2 ke = (8 +/- 5) h, T1/2 ka = (0.11 +/- 0.11) h, ku = (0.07 +/- 0.04) h-1, Xmax/f = (18 +/- 8) mmol. Relative bioavailability of effervescent tablet was 97.5% +/- 15.2% compared with common tablet. CONCLUSION: The two formulations were of bioequivalence. The methods used in this study might be applicable to other similar studies involving endogenous medicinal substances.