Age Changes in Rat Testicular Capsular and Parenchymal Δ13-Reductase and 15-Hydroxyprostaglandin Dehydrogenase Activities

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Abstract
Prostaglandin dehydrogenase (PGDH), Δ13-reductase, and total PGDH activities (the sum of the first two activities) were measured in rat testicular parenchymal and capsular preparations from 11 through 81 days of age. Δ13-Reductase activity closely paralleled PGDH activity and was substrate dependent except for the parenchymal activity at 61 and 81 days of age when something appeared to enhance its activity. All three activities, when expressed on a per milligram of tissue basis, were elevated at 11 days postpartum and then decreased to a low value at 21 days of age for the parenchyma and 21-32 days of age for the capsule. The elevated activity at 11 days of age suggested a possible elevation of enzyme activity by placental gonadotropins or possibly progesterone. Maximal activity was observed at 51 days of age for the parenchyma and 61 days for the capsules with diminished activities observed with advancing age except for the parenchymal Δ13-reductase activity. On a per milligram of tissue basis, the capsule demonstrated more enzyme activity than did the parenchyma with maximal activities being observed at 51 days of age. Possible control mechanisms were the following: substrate induction, gonadotropins, testosterone, or those factors regulating testosterone secretion.