The Ability of the Rat to Metabolize Myristoyl–Methionine: an Acylamino Acid with Potentially Useful Antibacterial Properties

Two experiments with Sprague–Dawley rats tested their ability to hydrolyse myristoyl–methionine (M–M) into myristic acid and l-methionine (M). In the first experiment, lasting for 3 days, male rats were orally administered [9,10-3H]myristoyl-l-[35S]methionine. The recovery of radioactivity was approximately 90% for both isotopes; 19% of the administered 3H was recovered in the urine and 16% in the faeces, while the recovered 35S activity was 13 and 12%, respectively. The balance of the radioactivity was found among the tissues, organs and blood. In the second experiment, male and female rats received soybean-based diets which were supplemented with either 0.305% M–M or 0.2% M (both diets contained equal amounts of M) for periods up to 4 weeks. The growth rate of the rats receiving the 0.305% M–M diets was slightly slower than that for the rats on the 0.2% M diet, but the difference was not statistically significant (P>0.05). The M–M rats had a transitory decrease in feed consumption, suggesting that palatability may have contributed to the growth difference and that a somewhat greater amount of M–M was necessary for the rat to attain the same growth rate as that produced by 0.2% M. When the amount of dietary M–M was increased to 3.05% M–M, a greater reduction in feed consumption and body weight gain was observed. This latter diet was an initial attempt to study the potential toxicity of M–M. None of the haematological, clinical chemistry or organ weight data suggested that M–M was overtly toxic per se, but longer-term feeding studies are needed to evaluate the potential toxicity of M–M more fully.