The modification of potential-dependent calcium channels in the membrane of secretory cells in a calcium-free medium

Effect of modification of potential-dependent calcium channels in cells of the upper lobe of the salivary gland in Chironomus larva has been ascertained in the Ca-free medium containing Ca-binding substances (EGTA or EDTA). It is shown that the inward current depends on the sodium transmembrane gradient. The amplitude of the inward sodium current decreases under the influence of verapamil as well as with an increase of external concentration of Ca2+ ions. The metabolic dependence of modified calcium channels as well as the pharmacological sensitivity are unchanged. Tau n of the sodium current through modified calcium channels increases insignificantly comparing with that of the calcium current. Maximum of the current-voltage relationship of the sodium current through modified calcium channels is shifted to a negative side by 10-15 mV as compared with the calcium current through native channels.     

Antioxidant activity of the drug distinol in vitro

Distinol, ionol and dimethylsulphoxide were investigated in model reaction of thermal oxidation of methyl oleate for their antioxidant activity and for their influence on the rate of malonic dialdehyde formation in the liver tissue of chicken with E-hypovitaminosis in vitro. It has been found that the level of antioxidant activity in the homogeneous system of methyl oleate oxidation permits arranging the preparations studied in a series: ionol > distinol > dimethylsulphoxide. Distinol inhibits peroxidation of lipids in the liver homogenates of chicken most efficiently. Its inhibitory effect is 4.6 times higher than that of dimethylsulphoxide and 1.3 times higher than that of ionol. No correlation was found between antioxidant activity of distinol in the homogeneous model system and its influence on peroxidation of lipids in biomembranes.     

Role of calcium in exocrine pancreatic secreation. VI. Characteristics of the paracellular pathway for divalent cations

(1) The transepithelial permeability for Ca2+ and Mg2+ in the isolated rabbit pancreas has been studied. (2) Values for the permeability of the unstimulated pancreas were obtained either by adding radioactive tracers to the bathing medium and measuring their concentration in the secreted fluid under steady-state conditions, or by analysis of the Ca2+ and Mg2+ concentrations in the secreted fluid after correction for protein-bound divalent cations. (3) Both methods give almost the same results: 27 and 26% for Ca2+ and 21 and 18% for Mg2+, respectively; both values being expressed as the percentage of the concentrations in the bathing medium. (4) The amounts of Ca2+ and Mg2+, appearing in the secretory fluid after correction for protein-bound cations, are linearly related to the extracellular Ca2+ and Mg2+ concentrations in the bathing medium, which indicates passive permeation. The two cations appear to pass through the paracellular route in their hydrated form. (5) Stimulation with carbachol or pancreozymin causes an increase in the paracellular permeability. This increase is approximately equal for the two divalent cations. Its time dependence and magnitude depend on the concentration of the stimulant rather than on the type of stimulant.