Influences of Age and Sexual Maturity on the Response of Renal Ornithine Decarboxylase Activity to Diabetes Mellitus

Summary

We have assessed the effect of age on basal renal ornithine decarboxylase (ODC) activity and on the response of this enzyme to streptozotocin-induced diabetes. Renal ODC activity was found to decline with age in both male and female rats. In addition, three distinct patterns of renal ODC activity were observed during the first three days of diabetes depending on the age of the rats. When expressed as a percentage of non-diabetic age-matched control animals, renal ODC activity was decreased in 23-25 day old male rats (24 ± 7 %), unchanged in the 30-35 day old (93 ± 11 %), and increased in rats older than 45 days (308 ± 9 %). These changes were similar in female rats.

To determine whether these age-dependent patterns were due to weight or to sexual maturity, weanling rats of both sexes were castrated and then allowed to grow to age 60-65 days before diabetes was induced. Despite similar growth rates as intact rats, the castrate diabetic rats had renal enzyme responses typical of 23-25 day old rats. Sexually immature rats of both sexes when treated with appropriate sex steroids for a short period prior to diabetes converted to a renal ODC response typical of older rats. Rats pastrated after puberty maintained an adult renal ODC activity response to diabetes.

These results demonstrate that the activity of renal ODC changes with aging and that the response of this enzyme to streptozotocin diabetes is age but not sex dependent. The age dependence of this response appears related to the sexual maturity of the animal.

Key-Words:

Ornithine Decarboxylase Activity - Streptozotocin - Diabetes - Sexual Maturity - Aging