Developmental expression of multiple forms of 3-hydroxy-3-methylglutaryl coenzyme A reductase mRNA in rat testes

The developmental expression of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, the enzyme that catalyzes the rate-limiting reaction of mevalonate formation, was investigated in rat testes. Adult testes were found to contain three distinct forms of HMG-CoA reductase mRNA of 4.8, 4.2, and 4.0 kilobases (kb) in length. In testes from 26-day-old rats the 4.8-kb species was the major form present. By 40 days of age, large increases in the levels of the testes-specific 4.2- and 4.0-kb forms occurred, with a small decrease in the amount of the 4.8-kb form. The level of the 4.8-kb form appeared to be associated with the level of testicular HMG-CoA reductase activity.