Effects of Methylene Blue on Respiratory Metabolism of the Rat

Abstract

Methylene blue exerts definite effects in the metabolism of excised tissue. 1 It is therefore of importance to determine the action of methylene blue in the intact animal. The respiratory metabolism of 6 rats was studied by means of a Haldane open circuit apparatus after various periods of fasting. Then 0.5 cc. M/100 methylene blue per 100 gm. of body weight was injected intraperitoneally. The CO₂ production and O₂ consumption were measured for varying periods during the following 48 hours. The results in all 6 animals bear a striking similarity. The composite graph depicts the observations of the 4 animals that were in the postabsorptive condition.

The graph discloses that there is a fall in the R.Q. which is followed by a subsequent rise. The early fall in the quotient is caused in part by a diminished production of CO₂ and partly by an increased consumption of O₂. The greater O₂ uptake indicates that the decreased production of CO₂ occurs despite an increased pulmonary ventilation. The fall of the R.Q. carries it to a value below 0.7 but the total R.Q. for the entire period of 48 hours in these 4 rats varied between 0.711 and 0.737.