Category Archives: Progesterone

Progesterone Implants Delay: DISCUSSION(3)

In women, there has been little evidence to indicate a sparing effect of oral contraceptive use on the age of menopause. One recent report indicates that women with a history of oral contraceptive use have lower cycle Day 3 FSH values than women with no prior history. Since this FSH value is believed to be predictive of the ovarian follicular reserve, these findings may suggest … Continue reading

Progesterone Implants Delay: DISCUSSION(2)

Thus, an age-related decline in the ovarian follicular pool is associated with alterations in the pattern of follicular development and steroidogenesis, with potential impacts upon neuroendocrine function and oocyte quality. In light of these previous observations, it is conceivable that there is a functional correlation between the dramatic effects of P4 implant treatments on the maintenance of regular estrous cyclicity and on the conservation of … Continue reading

Progesterone Implants Delay: DISCUSSION(1)

The onset of reproductive senescence in middle-aged female rats is associated with altered neuroendocrine regulation of gonadotropin secretion as well as changes in ovarian function. While it is difficult to determine whether neuroendocrine or ovarian impairments are primary causes of reproductive senescence, the findings from the present study indicate that the protective effect of successive P4 implant treatments on the loss of estrous cyclicity during … Continue reading

Progesterone Implants Delay: RESULTS(3)

Effects of Successive P4 Implant Treatments on Subsequent Patterns of Estrous Cyclicity during Aging Figure 4 depicts the incidence of regular estrous cyclicity in female rats treated with P4 implants, as compared with virgin controls. At 9 mo of age, only 21% of control females were regularly cyclic, the remainder displaying irregular cycles (14%) or persistent estrus (65%; data not shown). In contrast, rats previously … Continue reading

Progesterone Implants Delay: RESULTS(2)

Figure 2 depicts the daily patterns of serum LH levels in rats implanted with P4 for 3 wk as compared to regularly cyclic controls. During the estrous cycle, serum LH values at noon fluctuated between 103 ± 11 and 125 ± 5 ng/ml. Similarly low levels of LH were observed in P4-implanted rats. To examine in more detail the patterns of LH secretion in these … Continue reading

Progesterone Implants Delay: RESULTS(1)

Serum Patterns of P, E, and Gonadotropins in P4-Implanted Rats and in Cyclic Females Figure 1 depicts the daily patterns of serum E2 in rats during 3 wk of treatments with P4 implants (left panel), compared to those in cyclic females on different days of the estrous cycle (1200 h; right panel). Cyclic females exhibited elevated serum E2 (86 ± 6 pg/ml) at noon on … Continue reading

Progesterone Implants Delay: MATERIALS AND METHODS(4)

Influence of P4 Implant Treatments on the Subsequent Incidence of Regular Estrous Cyclicity After removal of the last implants at 8 mo of age, subsequent patterns of estrous cyclicity were determined by daily vaginal lavage for the next 4 wk. Rats that displayed prolonged cycles (6 or more days) of variable duration were considered to be irregularly cyclic, whereas those displaying more than 15 consecutive … Continue reading

Progesterone Implants Delay: MATERIALS AND METHODS(3)

Influence of P4 Implant Treatments on the Ovarian Follicular Reserve During the last implant treatment (at 8 mo of age), ovaries were collected from some female rats in each group to determine the influence of steroid implant treatments on the age-related loss of ovarian follicles. Ovaries were taken from P4-implanted rats (n = 5 per group) 20 days after administration of the last implants, and … Continue reading

Progesterone Implants Delay: MATERIALS AND METHODS(2)

Characterization of Circulating Hormone Levels during Implant Treatments The daily patterns of circulating hormones were examined in separate groups of 4-mo-old virgin rats (n = 6-10 per group) treated with P4 implants or empty implants. Consecutive blood samples (1.0 ml each) were obtained from these rats at 1000 h prior to implant placement, at 1800 h of that day, and at 1200 h on the … Continue reading

Progesterone Implants Delay: MATERIALS AND METHODS(1)

Animals Long-Evans virgin female rats (85 days old) were obtained from Charles River Laboratories (Portage, MI) and housed five per cage under standard vivarium conditions, with room temperature (24-26°C) and lighting (lights-on from 0500 to 1900 h daily) controlled throughout the study. Daily vaginal smears were taken from these rats to determine their estrous cycle patterns. Animals that exhibited at least three consecutive 4- to … Continue reading