On Digestive Proteolysis: Being the Cartwright Lectures for 1894Chittenden, R. H. (Russell Henry)
Science
On Digestive Proteolysis: Being the Cartwright Lectures for 1894
Chittenden, R. H. (Russell Henry)
Digestion; Digestive enzymes; Enzymes
It is thus evident that pure peptones, even when taken into the stomach
in fairly large amounts, and under conditions very favorable for rapid
absorption, pass into the circulating blood very slowly. Obviously,
however, one must not lose sight of the fact that when digestion is
under way and the volume of blood consequently increased, there may
be a corresponding rise in the rate of absorption. There is perhaps a
hint of this conclusion in the influence of alcohol on the absorption
of peptone as brought out by some of Brandl’s experiments. Thus, it
was found that when alcohol was added in considerable quantity to a
ten per cent. solution of peptone, the stomach-mucosa was greatly
reddened, while in two hours the absorption of peptone amounted to
11.8 per cent. But in any event, these results certainly do not favor
the view that the products of gastric digestion are absorbed as soon
as they are formed. It is, no doubt, quite different in the intestine,
but in the stomach, where pepsin-proteolysis occurs, we have, I think,
no grounds for assuming that either peptones or proteoses are rapidly
absorbed. Hence, it might perhaps be considered that the results of
pepsin-proteolysis in the living stomach are much the same as those
obtained in artificial digestion experiments.
Still, there are other differences between natural digestion and
artificial proteolysis than those connected with the possible
absorption of the more diffusible products of digestion. Thus, in the
living stomach there is an ever-increasing secretion of hydrochloric
acid, and perhaps also of pepsin, more or less proportional to the
extent of proteolysis. On this point Brandl’s experiments again give
us some light. Thus, it was found that the introduction of an aqueous
solution of peptone into the empty stomach led to the secretion of an
acid fluid containing on an average 0.24 per cent. HCl, while, under
similar conditions, the introduction of sugar or potassium iodide
was followed by the secretion of a fluid containing on an average
only 0.13 per cent. HCl. Further, the absolute amount of acid found
after the introduction of peptone was far greater than when sugar or
iodide was introduced, since peptone led to an increase of at least
fifty per cent. in the volume of fluid secreted. Hence, proteolysis in
the living stomach may give rise to such an increased production and
secretion of hydrochloric acid that formation of the terminal products
of gastric digestion may be greatly accelerated. That such in fact is
the case, I have no manner of doubt, but that it may result in the
complete conversion of the so-called primary and secondary proteoses
into peptone I very much question. In fact, such examinations as I have
made of the stomach-contents after a suitable test-meal have always
resulted in the finding of a relatively large amount of proteoses. To
be sure, true peptone may be detected and in fairly large amounts,
Public-domain text, read in full here on John Shaqi.
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