Effects of Testosterone on the Distribution of Carnitine, Acetylcarnitine, and Carnitine Acetyltransferase in Tissues of the Reproductive System of the Male Rat.

In an accompanying publication, we have shown that in most tissues there is an approximate correspondence between levels of carnitine acetyltransferase activity and concentrations of carnitine or acetylcarnitine (1). In addition, this correspondence may generally be related to the magnitude of the increase in fatty acid oxidation elicited by added carnitine in particular tissue preparations (1, 2). Thus heart muscle, skeletal muscle, and brown adipose tissue have high levels of transferase, carnitine, and acetylcarnitine, and mitochondria from these tissues show a large increase in long chain fatty acid oxidation in response to carnitine addition (l-3). In contrast, brain and kidney have considerably lower levels of these components and the effect of carnitine on fatty acid oxidation by particulate fractions from these tissues is less pronounced (3). Testis is an exception to both these generalizations in that carnitine acetyltransferase levels are unusually high relative to carnitine concentrations (l), and the magnitude of the metabolic response of testicular particulate fractions to added carnitine is low (3). We therefore decided to investigate testis and accessory sex tissues in more detail in an effort to determine the distribution of the components of the carnitine acetyltransferase system in various cell types. Data to be reported indicate that both transferase levels and carnitine concentrations in testis and in epididymus are under androgenic control, and that spermatozoa have the highest carnitine acetyltransferase activities of any cells thus far investigated.