Lymphocyte apoptosis in ovariectomized mice given progesterone and voluntary exercise.

BACKGROUND: At menopause, many women begin both exercise programs and hormone replacement therapy (HRT). Although the effects of estrogen on exercise behavior and immune functions have been well characterized, less is known about the behavioral and immunological consequences of progesterone (P) administration. The purpose of the present study was to describe the effect of P on running behavior and on lymphoid tissue cell viability and apoptosis in ovariectomized female mice.
METHODS: Adult female B6D2F1 mice were ovariectomized, allowed to recover for 1 week and implanted subcutaneously with 25 mg progesterone (n=42) or placebo pellet (n=42). Within hormone treatment, mice were randomized to running wheels or no running wheel conditions. After 21 days of wheel running and hormone exposure, mice were sacrificed for measurements of body weight, tissue weights, and thymocyte and splenocyte apoptosis, necrosis and viability with annexin-V FITC and propidium iodide by flow cytometry.
RESULTS: P treated mice were heavier than placebo controls at sacrifice (p<0.001). Irrespective of hormone condition, mice increased the volume of spontaneous activity over time (p<0.001). Within the thymus, there were no differences by hormone or running condition on percent apoptosis, necrosis and viability. In the spleen, P marginally increased percent apoptosis (p<0.05) and reduced percent viability (p<0.001). Serum levels of P were higher in the hormone replaced mice compared with placebo mice (p<0.001) and in running compared with sedentary mice (p<0.01).
CONCLUSIONS: P replacement in ovariectomized mice does not alter running volume relative to placebo animals. P alone was associated with a small increase in splenocyte apoptosis. The clinical relevance for postmenopausal women of lymphocyte viability changes needs to be determined.