Protein Biosynthesis in the Testis: II. Role of Adenosine Triphosphate (ATP) in Stimulation by Glucose

Abstract

The test is is dependent upon glucose as a source of energy and glucose is known to stimulate protein biosynthesis in testes from mature rats but not in testes from immature rats. The hypothesis that glucose increased testicular protein biosynthesis by stimulating the synthesis of adenosine triphosphate (ATP) was examined by measuring the concentration of this nucleotide in rat testes incubated under a variety of conditions with and without glucose. It was found that the concentration of ATP in rat testis is 1.50 ± 0.02 μmoles/g wet weight, which i s close to values reported for a number of cells and tissues. The concentration of testicular ATP falls rapidly during 30 min of incubation. The hypothesis that glucose increases protein biosynthesis by increasing the production of ATP was supported by the following observations: 1. Glucose prevents the decline in testicular ATP seen during incubation in vitro and increases the rate of protein biosynthesis during the same period of time. The values for ATP and protein biosynthesis are increased above control values (incubated without glucose) to approximately the same extent. Moreover, addition of glucose after incubation for 30 min without this substrate increases both the concentration of ATP and the rate of protein biosynthesis. 2. Incubation of testis with fructose results in a concentration of ATP and a rate of protein biosynthesis which are both approximately twice those found in control (incubated without fructose). In each case these values are approximately half of those observed with glucose. Ribose neither prevents the expected decrease in ATP levels during incubation nor increases the rate of protein biosynthesis. 3. Janus green B, which inhibits the extranuclear synthesis of ATP, prevents the increases in protein biosynthesis and ATP usually seen when glucose is present in the incubation medium. 4. Incubation of rat testis under anaerobic conditions prevents the increases of ATP and protein biosynthesis usually seen in the presence of glucose. 5. Glucose increases neither the concentration of ATP nor the rate of protein biosynthesis in testes of immature rats. These observations suggest that the effect of glucose in maintaining levels of testicular ATP during incubation in vitro may be a major factor in the mechanism by which the hexose stimulates testicular protein biosynthesis in vitro. (Endocrinology83: 86, 1968)