Abstract
ABSTRACTThe aim of our study was to understand whether ovarian steroid hormones, and their response to the metabolic hormones leptin and IGF-I leptin, could be involved in the control of mink reproductive aging via changes in basal release of ovarian progesterone and estradiol. For this purpose, we compared the release of progesterone and estradiol by ovarian fragments isolated from young (yearlings) and old (3-5 years of age) minks cultured with and without leptin and IGF-I (0, 1, 10 or 100 ng/ml). We observed that isolated ovaries of older animals produced less progesterone but not less estradiol than the ovaries of young animals. Leptin addition stimulated estradiol release by the ovarian tissue of young animals but inhibited it in older females. Leptin did not influence progesterone output by the ovaries of either young or older animals. IGF-I inhibited estradiol output in young but not old animals, whereas progesterone release was inhibited by IGF-I irrespective of the animal age. Our observations demonstrate the involvement of both leptin and IGF-I in the control of mink ovarian steroid hormones release. Furthermore, our findings suggest that reproductive aging in minks can be due to (a) reduction in basal progesterone release and (b) alterations in the response of estradiol but not of progesterone to leptin and IGF-I.
Highlights
The age-dependent reduction in animal and human fecundity can be due to the reduced release of ovarian steroid hormones in females – mainly estrogen, estradiol and the progestogen, progesterone
The aim of our study was to understand whether ovarian steroid hormones and their response to the metabolic hormones leptin and insulin-like growth factor I (IGF-I) could be involved in the control of mink reproductive aging, i.e. whether aging can be associated with changes in the basal release of ovarian progesterone and estradiol and in their response to IGF-I and leptin
The ovarian tissue isolated from older animals and cultured without leptin or IGF-I (0 ng/ml) released significantly less progesterone than the tissue isolated from the ovaries of young minks (Fig. 1A,C)
Summary
The age-dependent reduction in animal and human fecundity (reproductive aging) can be due to the reduced release of ovarian steroid hormones in females – mainly estrogen, estradiol and the progestogen, progesterone. These hormones promote ovarian follicullogenesis, oogenesis, ovulation and gravidity (Broekmans et al, 2009; Dias et al, 2014; Finch, 2014; Hale et al, 2014). The involvement of metabolic hormones leptin and IGF-I in the control of reproduction has been shown only in a small number of species (rodents, cows, pigs, chicken and humans; Sirotkin, 2014; Sirotkin et al, 2014) The role of these hormones in the control of ovarian functions in other species remains unknown
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