Inhibitory action of insulin on the acid secretion of the stomach

Abstract

The action of insulin upon the gastric secretion of man and dog while keeping intact the vagal innervation is well known. On the contrary, the effects of this substances on the cat is a point of discussion.

In man and dog —with vagii not anesthetized— the pa- renteral administration of insulin, not mattering the way used, produces an increase of gastric secretion which reaches its máximum in 30-40 minutes.

In the cat, Fogi, Strom and UvnAís, observed that insulin has no effect over the gastric secretion. GROSSMAN atributes the divergence to the fact that they used insufficient quantities of insulin to provoke an hypoglycemia capable of stimulating the vagal centers.

We find it interesting to study again this subject in order to make clear the differences.

We used cats in which we made a atotal bag of the sto­ mach» conserving the vagal innervation. These cats were anesthetized with dial or chloralose, sometimes only intravc- nous injection of insulin' was used using doses reaching 10 units per kg of weight. Other times a continuous intra- venous injection was used, administrating up to 0.56 units per kg of weight per minute. We studied the action of insulin over the basal secretion of the stomach and over the secretion induced by the continuous injection of histamine.

In Table I we registerod the effects of insulin as the only stimulant over the basal secretion of the stomach. In it we see that not mattering the great quantities of insulin in- jected the secretion lightly increases (generally we do not find basal secretion). The quantities of juice obtained are much lower than those obtained with histamine in cats in the same conditions.

There is no free HC1 in the juice produccd by insulin and the total acidity is always maintained below that induced by histamine acting over the same period. On the contrary, the total Cl“ increases in a similar proportion to that of the juice induced by histamine.

In table II we see the results of the action of insulin over the constant gastric secretion induced by histamine. In all our cats, the insulin reduces noticeably the volume of the segregated juice, reaching the lowest valúes 40-60 minutes later.The free HC1 and the total acidity descend noticeably also.

In all our experiments, insulin caused a decrease in the glycemia although in different grades. In several of them itreached 30 mg glucose per 100 c. c. of blood.

Using insulin as the only stimulant does not produce in our cats a secretion able to be compared to that induced by histamine.

The observations of Uvnas and colaborators agree with our results, not mattering Grossman’s objections to them. Theglycemia valúes reached in our experiment were as high as 30 mg and KNELLER and NassET find in dogs that hypogly- cemias between 25 and 50 mg are the best stimuli for secretion.

We atribute the lack of secretion in our cats to the fact that observations were made under anesthesia. The studies of the action of insulin on the gastric secretions of dog and man hadj been made generally in individuáis without anesthesia and there lies the difference (Quigley and Templeton ; Fogi and

Uvnas).
Insulin, in our experiments, lowers the constant secretion

induced by histamine, the same thing that Karvinen and I<AR- vonen found in unanesthetized dogs with the Heindenhain stomach.

In anesthetized cats, but with innerved stomach, insulin provokes a lowering of histamine secretion. We distinguish a double action for the hypoglycemia provoked by insulin : one Peripherie over the parietal cells of the stomach and another central stimulating action that is blocked by anesthesia and needs the concurrence of the vagii.

From our observations results that insulin exerts over the gastric secretion of the cat the same action as over the dog’s. The increase of the stomach secretion originated by the ex- citation of the vagal centers by insulinic hypoglycemia obser- ved in man and dog without anesthesia is not produced in the cat or in the dog anesthetized with barbiturates or chloralose.

The secretion produced by histamine is inhibited by the action of insulin as much in the dog as in the cat. The inhibitory action observed in dogs without vagii is also produced as wesee, in the cat with vagii but anesthetized. Insulin’s action over the gastric secretion will be double for us : there is acentral stimulating action over the gastric secretion that dis- sapears by the anesthesia and which needs the concurrence of vagii; another with peripheric and direct action over the parietal cells. without need of the vagii and that is not altered by the anesthesia and has an inhibitory action.