Influence of cortisol on the nitrogen balance in rats

Abstract

It is a well-known fact that cortisol retards growth but its mode of action is not as well established.

In the present study and as a contribution to this knowledge, we have studied the effect of cortisol injection upon the digestive and metabolic utilization of alimentary nitrogen in rats.

The technique followed was that of Thomas Mitchell based upon the nitrogen balance in growing rats. Two experiments were carried out. In the first, a group of 24-day-old rats was Injected with 2 mg of cortisol per rat for seven consecutive days. A control group was injected with saline solution under equal conditions.

In the second experiment, a group of 24-hour-old rats was injected once with 1 mg of cortisol. A control group was injected with saline solution under equal conditions. After 28 days of treatment the rats injected with cortisol only once had attained the same weight as the rats of the previous experiment. At this time the nitrogen balance of both groups was determined. But in this experiment a third control group was added. The experiment consisted of one group injected with cortisol, another control group with rats of the same age but greater weight and a third group of equal weight but of different ages.

From our experiments we can conclude that cortisol injected once at birth has as much effect on the retardation of growth as it does injected into older rats over a period of several days. On the one hand this retardation is due to the action upon the ingesta and, on the other hand, to the poorer metabolic utilization of nitrogen. However, it does not seem to affect the digestive use of nitrogen in the food.