Effect of Intramuscular Administration of Antibiotics on the Oxygen Consumption of Normal and Hyperthyroid Rats

¹ From the Departments of Biochemistry and Animal Husbandry, Purdue University, Lafayette, Indiana

The oxygen consumption of normal and hyperthyroid albino rats was measured before and after the intramuscular injection of 1.2 mg (0.2 ml of solution) of procaine penicillin G, Aureomycin or Ilotycin. The final measurements were observed at either 1- or 3-hour intervals after the injection. The antibiotics caused a statistically significant decrease in the rate of oxygen consumption in both normal and hyperthyroid rats. This effect diminished with time. Similar effects were observed with procaine penicillin G after oral administration by stomach tube. It is suggested that antibiotics may somehow influence the endocrine system, possibly the level of circulating thyroxin. Such studies are in progress.