A comparison between hormone levels and T lymphocyte function in young and old rats
1Department of Physiology, Michigan State University, East Lansing 48824.
Mechanisms of Ageing and Development
|December 31, 1991
Summary
Aging reduces thymus function, linked to lower thyroxine (T4) and growth hormone (GH) levels in rats. These hormonal changes may cause age-related declines in T lymphocyte function and thymocyte proliferation.
Area of Science:
- Endocrinology
- Immunology
- Aging Research
Background:
- Hormone secretion changes with age, potentially affecting thymus function.
- The relationship between endocrine changes and thymic function during aging requires further investigation.
Purpose of the Study:
- To investigate the relationship between circulating hormone levels and T lymphocyte function in aging rats.
- To determine how age-related changes in prolactin (PRL), growth hormone (GH), thyrotropin (TSH), thyroxine (T4), and triiodothyronine (T3) affect thymic and splenic immune responses.
Main Methods:
- Measured PRL, GH, TSH, T4, and T3 levels in young and old Long-Evans male rats.
- Assessed thymocyte and splenocyte proliferation in response to mitogens and lymphokines.
- Correlated hormone levels with T lymphocyte functional indices.
Main Results:
- Old rats exhibited significantly lower GH and T4 levels compared to young rats.
- Thymic cell numbers were drastically reduced in old rats, while spleen cell numbers remained unchanged.
- Thymocyte proliferation was diminished in old rats, but splenocyte IL-2 production was not significantly different.
- Serum T4 levels correlated with thymocyte count and proliferation, while GH inversely correlated with splenocyte IL-2 release.
Conclusions:
- Reduced T4 and GH secretion in aging rats may contribute to age-related declines in thymic function.
- Hormonal changes during aging appear to impact thymic-dependent immune functions.
