14 



Endocrine Factors in Food Absorption 



of the intestinal mucosa in general but by stimulation of the chemical mecha- 

 nism in the intestinal mucosa which is responsible for preferential absorption. 

 Other experiments ruled out as factors which significantly accelerate absorp- 

 tion: relative starvation, depletion of carbohydrate, a rise in body temperature, 

 an increase in basal metabolism, a rise in the velocity of the blood flow, ac- 

 celeration of gastric emptying, stimulation of intestinal peristalsis, and adjust- 

 ment to an increased food intake. The last factor was shown to be unimportant 

 by an experiment according to which, when food intake of hyperthyroid rats 

 was limited to that of normal rats, the rate of absorption for dextrose remained 



TABLE 2 



Intestinal Absorption of Various Food Elements in Normal 

 AND IN Hyperthyroid Female Rats 



* Standard deviation. 



abnormally high (252 ± 10 mg.). A separate experiment with repeated intra- 

 gastric feedings proved that the increased rate of absorption persisted for at 

 least three hours after administration of dextrose was begun. 



Experiments were carried out on normal and on hyperthyroid rats to test 

 a possible mechanism of action of the thyroid hormone in intestinal absorp- 

 tion based on the theory of Verzar that preferential absorption of sugars and 

 fats is due to phosphorylation in the intestinal mucosa. For the purpose of 

 inhibiting phosphorylation locally in the mucosa, 50 mg. of phlorizin were 

 added to a solution of dextrose, to oleic acid, and to olive oil. The phlorizin 

 reduced the absorption of these substances (table 3) to the same level in normal 

 and in hyperthyroid rats— an indication that the entire mechanism of prefer- 

 ential absorption of these substances was paralyzed. This conclusion was con- 

 firmed by the observation that the reduced rate of absorption for glucose in- 

 duced by phlorizin was equal to that for xylose, which is absorbed by simple 

 diffusion. The possibility that phlorizin may decrease intestinal absorption 

 in general was ruled out by showing that it did not affect the absorption of 

 calcium lactate. 



In an effort to elucidate further the mechanism of selective intestinal absorp- 



