CREATINE SYNTHESIS AND TRANSPORT-SYSTEMS IN THE MALE-RAT REPRODUCTIVE-TRACT

Previous studies from this laboratory showed that high levels of guani dinoacetate methyltransferase are present in mouse testis and epididym is, whereas guanidinoacetate methyltransferase mRNA and protein are no t detected in seminal vesicles where large amounts of creatine (Cr) an d phosphocreatine are found (Lee et al., Biol Reprod 1994; 50:152-162) , To further investigate the origin(s) of Cr in the male reproductive tract, the expression patterns of the three enzymes and a transporter involved in Cr metabolism were examined with rat reproductive tissues. Western blot analysis showed that expression of L-arginine:glycine am idinotransferase was limited to the kidney. On the other hand, high le vels of the mRNAs for both guanidinoacetate methyltransferase and S-ad enosylhomocysteine hydrolase were expressed in the testis and epididym is as well as the liver and kidney. Cr transporter mRNA was highly exp ressed in the seminal vesicle and vas deferens. These results suggest that the source of Cr in the male reproductive tract varies depending on the tissue; in the testes and epididymides, Cr is synthesized from guanidinoacetate, while in the seminal vesicles, Cr is transported fro m blood. Previous and present findings suggest the importance of Cr me tabolism and/or transport for reproductive functions.