Treatment of rats with 0.5-25 /zmol/100 g body weight of colchicine for 1 h or more caused an inhibition of hepatic protein synthesis. This effect was not seen if the animals were exposed to colchicine for less than 1 h. The delayed inhibition of protein synthesis affected both secretory and nonsecretory proteins. Treatment with colchicine (15 /zmol/100 g) for I h or more caused the RNA content of membrane-bound polysomes to fall but did not change the polysomal profile of this fraction. By contrast, the total RNA content in the free polysome cell fraction was increased, and this was due to the presence of more ribosomal monomers and dimers. Electron microscope examination of the livers from rats treated for 3 h with colchicine showed an accumulation of secretory vesicles within the hepatocytes and a general distension of the endoplasmic reticulum. Administration of radioactive Lleucine to the rats led to an incorporation of radioactivity into two forms of intracellular albumin which were precipitable with antiserum to rat serum albumin but which were separable by diethylaminoethyl-cellulose chromatography. One form has arginine at the amino-terminal position and is proalbumin, and the other form, which more closely resembles serum albumin chromatographically, has glutamic acid at its amino terminus. Only proalbumin was found in rough and smooth endoplasmic reticulum fractions and in a Golgi cell fraction which corresponds morphologically to mostly empty and partially filled secretory vesicles. However, in other Golgi cell fractions which were filled with secretory products, both radioactive proMbumin and serum albumin were found. This indicates that proalbumin is converted to serum albumin in these secretory vesicles just before exocytosis. Colchicine delayed the discharge of radioactive albumin from these filled secretory vesicles and caused an accumulation of both proalbumin and serum albumin within these cell fractions. KEY WORDS albumin proalbuminThe effects of colchicine on the physiology of secretion Golgi 9 colchicine the liver and on the secretion of plasma pro-400 J. CELL BIOLOGY 9 The Rockefeller University Press 9

We performed simultaneous, ambulatory monitoring of luminal pH in the stomach and in the duodenum in 20 healthy volunteers. The objectives were to determine normal pH ranges and patterns and the influence of food and posture on pH, and to study spontaneous alkaline shifts in the fasting stomach. Antimony electrodes were placed in the antrum and duodenum (second portion) under fluoroscopy. The pH values were recorded every 4 s and the data were analyzed by computer. During daytime and nighttime, when fasting, the gastric pH was generally less than pH 2. Eating increased the peak gastric pH to 4.1 ± 0.2. Alkaline episodes (pH ≧ 4 for 60 s or more) occurred in all subjects frequently in the early morning hours; the mean frequency was 13.3 ± 2.7 per 24-hour period. Duodenal pH was generally neutral (pH > 6 for 66% of the study period). There were 156 ± 20 acid spikes (pH < 4, duration 15 s) per 24 h. Results indicate that long-term, ambulatory pH-metry in stomach and duodenum is possible, that eating and posture do influence pH profiles and that spontaneous alkaline pH shifts regularly occur in healthy individuals.

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