Tho elimination and toxicity of caffein in nephrectomized rabbits

In experiments on the elimination of caffein in rabbits and guinea pigs carried out by the writers 1 in this laboratory recently it was found that much larger amounts of caffein were recovered from the gastro-intestinal canal when these animals were fed oats than when carrots were given. Since greater quantities of urine are secreted on a diet of carrots than on one of oats, it seemed probable that the excretory function of the gastro-intestinal canal might be stimulated to greater activity in order to compensate for the diminished diuresis when oats were fed. The elimination of caffein into the gastro-intestinal canal after the removal of both kidneys ought to be greater, therefore, than in normal animals.

In experiments which were performed with caffein which was given subcutaneously to rabbits after double nephrectomy, the following results were obtained: The amounts recovered at the end of about 22 hours from the contents of the stomach and intestines varied between 7.7 per cent. and 11.78 per cent., which is two to three times greater than was found in normal rabbits, much larger amounts being present in the intestines than in the stomach. In one rabbit which died seven hours after caffein was injected subcutaneously, about 10½ per cent. were recovered from the intestines and about half this amount was obtained from the contents of the stomach.

The total amount of caffein eliminated in nephrectomized rabbits in about 22 hours was approximately equal to that eliminated by the gastro-intestinal canal and kidneys combined of normal rabbits during an equal period of time, thus showing that the stomach and intestines acquire much greater power of elimination after the kidney is removed.

Observations were also made on the toxicity of caffein in nephrectomized rabbits.