Volume-activated chloride currents from human fibroblasts: blockade by nimodipine.

The whole-cell patch clamp technique was used to identify and to characterize volume-activated Cl- current (ICl(vol)) in fibroblasts derived from human periodontal ligament. During osmotic cell swelling, the cells exhibited an outwardly rectifying current, which was dependent upon the concentration of external Cl-. The anion permeability sequence of the chloride channel for anions was as follows: SCN- > I- > Br- > Cl- > F- > methanesulphonate > gluconate. Being an inhibitor of Cl- channels and Cl-/HCO exchanger, 4,4'-diisothiocyanato-stilbene-2,2'-disulfonic acid (DIDS) inhibited the currents with a voltage-dependence (EC50 57 micromol/l at +80 mV), and 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB), a carboxylate analogue Cl- channel blocker, showed the reversible suppression of the currents in a dose-dependent manner (EC50 = 59 micromol/l). Nimodipine, a selective dihydropyridine Ca2+ channel blocker suppressed ICl(vol) (EC50 = 66 micromol/l) and the effects were quite similar to those of NPPB. Nifedipine, another DHP blocker also inhibited the currents but with lesser efficacy (EC50 = 139 micromol/l). The removal of external Ca2+ or the addition of Cd2+ in the bath solution did not affect the blocking effects of nimodipine on ICl(vol). These findings demonstrate that the human fibroblasts ICl(Vol) was suppressed by nimodipine in an extracellular Ca2+-independent way. These results may provide, at least in part, an explanation for the Ca2+-independent decrease in Cl-/organic osmolytes efflux and RVD responses by nimodipine in some cell types.

Radon concentrations in groundwater in Busan measured with a liquid scintillation counter method.

In this paper, we present the first measurement of radon concentrations in drinking groundwater from private and public deep-bored wells located in the south-eastern area of Korea. The measurements were carried out on 439 samples by using a liquid scintillation method. The results show that the radon concentrations of the samples range from 0 to about 300 Bq l(-1). We find that Sasang ward shows the highest median value of radon concentration among 13 different wards, while Jung ward has the lowest. We find that the radon concentrations are highly dependent on the type of geological rock aquifers.

Measurement limits to 134Cs concentration in soil.

We investigate the caesium concentrations in soils in mountain areas near Gori nuclear power plant in Korea, focusing on the measurement limits to the (134)Cs. In order to lower the minimum detectable amount (MDA) of activity for the (134)Cs, we have used the ammonium molybdophosphate (AMP) precipitation method to get rid of the (40)K existing in natural radioactivity, which reduces the MDA activity about 10 times smaller than those without the AMP precipitation method. The MDA results for the (134)Cs were found to be in the range between 0.015 and 0.044 Bq/kg-dry weight. In order to diminish the background, we also have measured a part of the soil samples in Yangyang, a small town in the east coast of Korea. However, it turns out that in order to detect the (134)Cs in the samples the MDA should be reduced to the level of mBq/kg-dry weight.