Gastric Juice

Gastric Juice. Under G. j. in physiology is meant the juice secreted by the fundic part of the gastric mucosa; the pyloric part of it, however, secretes a small amount of viscous alkaline so-called pyloric juice. In clinical practice, gastric juice is mostly incorrectly used to mean gastric contents, which is in essence not pure G. j. (of which we are speaking here) but a mixture of G. j. with some remnants of test food; research of such gastric contents does not give an idea of pure G. j. Pure G. j. is a colorless and transparent, like water, liquid without odor, but with sharply acidic reaction and strongly acid taste due to the content of free HCl in G. j., the quantity of which varies in humans from 0.3% to 0.5%, and in dogs up to 0.6% and even, according to London, up to 0.7%. - The specific gravity of G. j. is low: 1.003-1.006 in dogs and 1.008-1.009 in humans. The freezing point depression varies from 0.52° to 1.21°. The amount of solid substances is not more than 0.3-0.4% and varies depending on the type of gastric secretion stimulant. Of inorganic substances besides HCl, gastric juice contains NaCl, KCl, NH₄Cl, phosphates, sulfates and a small amount of hydrocyanic acid. Of organic substances G. j. contains protein bodies, partly in the form of nucleoproteins, and three enzymes: 1. Pepsin - an enzyme acting only in an acidic medium and breaking down protein bodies to the stage of peptones, with the optimum action of pepsin being about 0.15-0.2% HCl. The pepsin content, usually determined by the method of Mett, varies depending on the type of secretion stimulant; thus, the juice secreted in response to milk is poorest in pepsin, the bread juice is richest, and the meat juice occupies an intermediate position. 2. Rennin, or rennet enzyme, curdles milk in acidic, neutral, and slightly alkaline media. I. P. Pavlov, unlike other authors, believes that the rennet action of G. j. belongs to the same enzyme as the peptic one. -3. Lipase splits only emulsified fats. A number of authors have found this property in G. j. obtained from an isolated stomach. However, other authors, in particular Boldyrev, decisively deny the lipolytic ability of G. j., and some attribute it to HCl. The acidity of G. j. depends on its HCl content, the quantity of which varies individually. Until recently, Pavlov's school held the opinion that G. j. in the same individual is always secreted with the same concentration of HCl. The observed fluctuations in the acidity of G. j. were explained by this school as being due to the speed of juice secretion; thus, some authors believe that the acidity of the juice is connected with how quickly G. j. flows over the gastric mucosa covered with gastric mucus, which neutralizes a larger part of HCl the slower the secretion, and vice versa. However, Pavlov's view that G. j. is prepared by the glands with the same acidity and that all deviations can only concern the amount of G. j. was not shared by all researchers. To Pavlov's view also joined a part of clinicians, nevertheless another part of them admitted that in pathological function acidity can be disturbed in both directions, i.e., they admitted that it can be even below 0.3% and above 0.5% HCl. In connection with the recent works among physiologists, including former Pavlov's collaborators, voices began to be heard (Babkin), indicating that "the question of juice acidity is the next question", and even the opinion is expressed (Savich) that now it is already "impossible to consider acidity only a function of the speed of secretion". Clinicians, not having the technique for obtaining pure G. j., until recently could not present direct evidence confirming this variability, and only with the discovery of histamine secretion this variability somehow receives real proof. Already now after histamine, G. j. is obtained which, in its acidity, exceeds (comparatively rarely) the maximum acidity for humans, or juice with lower acidity (which is more often) than is normal. True, in the latter cases the neutralizing role of the juice mucus, usually mixed in significant quantity with gastric juice with reduced acidity, is not yet clear. Nevertheless, from a practical point of view, one can already speak of both hypochlorhydria and hyperchlorhydria (see Stomach - motor and secretory disorders). - Besides the above-mentioned inorganic and organic substances in pure G. j., one can always find flakes of mucus secreted by the epithelium of the gastric mucosa. Already in normal conditions, the first portions of secreted G. j. are rich in it, but the admixture of mucus is especially abundant in pathological cases, mainly in the catarrhal condition of the stomach. In these cases, G. j. becomes to one degree or another turbid, becomes viscous and acquires a whitish-grayish color. Already from the above it is seen that in pathological conditions G. j. changes. This change most often concerns its quantity, and from this point of view cases are distinguished with decreased (hypochilia) and with sharply increased (hyperchilia) secretion. - To the changes in the composition of G. j. must also be included cases with increased mucus content, observed mainly in gastritis. As for changes in the content of enzymes, it should be noted that changes in their content only to some degree go parallel with changes in acidity, in general the secretion of enzymes is preserved longer and does not change as sharply as the acidity of G. j. The chloride content in G. j. in normal conditions varies from 0.5% to 0.65% Cl. Katsch and Kalk consider the secretion of chlorides a separate, independent function of the stomach from the secretion of HCl. In connection with this, much data has accumulated indicating a very stable content of total chlorides in G. j. both in normal conditions and usually in pathological cases. In general - it is considered that the higher the chloride content, the better the glandular apparatus of the stomach is preserved, and conversely¹- a low percentage of them is observed mostly in a sharp violation of the function of gastric glands (see also Stomach - physiology, research methods and secretory disorders).