Longitudinal studies of estrous cyclicity in C57BL/6J mice: III. Dietary modulation declines during aging.
Dietary modulation of estrous cyclicity was studied throughout the reproductive lifespan to assess the stability of age-related changes in cyclicity and to probe underlying mechanisms. Animals were fed a standard diet or an isocaloric breeder diet that differed in nutrient composition to promote fecundity. In young mice, the breeder diet more than doubled the frequency of short (4-day) cycles, and, as a result, increased the total number of cycles during the cycling lifespan by 10%. Dietary potentiation of short cycles disappeared between 7 and 9 months of age, and most subsequent age-related changes in cyclicity were resistant to dietary influence. The breeder diet had no effect on the transition from 4- to 5-day cycles, the onset of acyclicity, or on the incidence or duration of persistent vaginal cornification. It only delayed the increase of very long (greater than 5-day) cycles by 1 month. These results show that most age-related changes in cyclicity are not influenced by dietary differences that affect cyclicity in young mice, and that diminished responsiveness to dietary variation is among the earliest age-related changes in the reproductive system. In addition, the results suggest that differences in cycle frequency and, presumably, in cumulative exposure to pre-ovulatory elevations of ovarian steroids do not influence the cycling lifespan in this strain of mouse.
Nelson
J F
JF
Department of Obstetrics and Gynecology, McGill University, Montrea, Quebec, Canada.
Goodrick
G
G
Karelus
K
K
Felicio
L S
LS
D000367:Age Factors; D000375:Aging / Q000502:physiology*; D000818:Animals; D001835:Body Weight; D004032:Diet; D004971:Estrus / Q000502:physiology*; D005260:Female; D005527:Food, Fortified; D051379:Mice; D008810:Mice, Inbred C57BL