Patch-clamp study of rubidium and potassium conductances in single cation channels from mammalian exocrine acini

Single-channel current recordings were carried out on excised inside-out patches of baso-lateral plasma membrane from exocrine acinar cells. The mouse pancreas and submandibular gland as well as the pig pancreas were investigated.In the mouse pancreas the voltage-insensitive Ca²⁺-activated cation channel was studied. Single-channel current-voltage (i/v) relationships were studied in symmetrical Rb⁺-rich solutions and in asymmetrical Rb⁺/Na⁺ and Na⁺/Rb⁺ solutions. In all cases the i/v relations were linear and had the same slope representing a single-channel conductance of about 33 pS which is identical to that previously obtained with symmetrical Na⁺ solutions or asymmetrical Na⁺/K⁺ solutions.In the mouse submandibular gland and the pig pancreas the voltage and Ca²⁺-activated K⁺ channel was studied. The outward currents observed after depolarization in the presence of quasi-physiological Na⁺/K⁺ gradients were immediately abolished when all the K⁺ in the bath fluid was replaced by Rb⁺ (bath fluid in contact with inside of plasma membrane). This effect was immediately and fully reversible upon return to the high K⁺ solution.The voltage and Ca²⁺-activated K⁺ channel was also studied in asymmetrical K⁺/Rb⁺ and Rb⁺/K⁺ solutions. In the first case inward (K⁺) currents could be observed but not outward (Rb⁺) currents, while in the other case inward (Rb⁺) currents could not be seen whereas outward (K⁺) currents were measured. The current-voltage relationships were approximately linear and the null potential was close to 0 mV in both situations. In contrast the null potential for current through the K⁺ channel in the presence of asymmetrical Na⁺/K⁺ or Li⁺/K⁺ solutions was about –70 mV and with reversed gradients about +60 mV.Outward K⁺ currents of reduced size (through the voltage and Ca²⁺-activated K⁺ channel) could be observed when the bath fluid contained 75 mM K⁺ and 75 mM Rb⁺, but not (in the same membrane patches) when 150 mM Rb⁺ and no K⁺ was present.It is concluded that the large voltage- and Ca²⁺-activated K⁺ channel has an extremely low Rb⁺ conductance. It is possible, however, that the permeability for Rb⁺ may be about the same as for K⁺. The voltage-insensitive Ca²⁺-activated cation channel does not discriminate between K⁺ and Rb⁺.     

Occurrence of saxitoxin and other toxins in the liver of the pufferfish Takifugu pardalis

Highly toxic livers of the pufferfish Takifugu pardalis were extracted with acidic ethanol. The toxins extracted were partially purified by chromatography on Bio-Gel P-2 and then Bio-Rex 70, resulting in separation into three fractions I, II and III. Ratios of total mouse units per fraction were approximately 0.1:100:0.01, respectively, with tetrodotoxin (TTX) as standard. By TLC, electrophoresis and a TTX analyzer, Fr. II was identified as TTX and, unexpectedly, Fr. III as saxitoxin, while Fr. I remains unidentified.     

Epidemiological follow-up study of Japanese thorotrast cases.

The authors conducted a follow-up study on 243 Thorotrast-administered war-wounded ex-servicemen in 1975, after a lapse of 30 to 38 years from Thorotrast injections, and found 18 cases of malignant hepatic tumor, 15 cases of other malignant tumors, 2 cases of blood diseases, and 9 cases of liver cirrhosis in 224 cases who had been given Thorotrast intravascularly. The incidence of hepatic and other malignant tumors, blood diseases, and liver cirrhosis was significantly higher than in the controls. The total number of deaths in the Thorotrast-administered cases was also significantly higher than in the controls. In the remaining 19 cases who had been given Thorotrast by a route other than intravascularly, no fatal case related to Thorotrast administration was discovered. In the living cases, however, one sarcoma was observed to have developed at the site of the Thorotrast injection.