Ovariectomized female monkeys were injected with saline, estradiol, or estradiol
ID: 180727 • Letter: O
Question
Ovariectomized female monkeys were injected with saline, estradiol, or estradiol plus progesterone. At 24 hours after the injection, the animals were killed and their pituitaries Were incubated in the presence and in the absence of LH - RH. Following incubation, the of LH in the incubation medium was determined by radioimmunoassay. Describe how these results are likely to be important for the regulation of ovulation during the normal menstrual cycle of the monkey. Daily injections of FSH into an immature female Nat will ovulation will not occur in FSH treated animals that lack a pituitary gland. Describe the mechanism responsible for induction of ovulation by FSHExplanation / Answer
1. The menustral cycle results from a finely tuned interplay of hormones secreted by the ovaries, the anterior pituitary and the hypothalamus.
2. During the early and middle follicular phases, FSH stimulates the granulosa cells to proliferate and secrete estrogen and LH stimulates the theca cells to proliferate and produce the androgens that the granulosa cells use to make estrogen.
a. During this period, estrogen exerts a negative feedback on the anterior pituitary to inhibit the secretion of gonadotrophins.
b. Estrogen may also inhibit secretion of GnRH by the hypothalamus
c. Inhibin preferentially inhibits FSH secretion
3. During the late follicular phase, plasma estrogen becomes high enough to elicit a surge of LH, which then causes, via the granulosa cells, completion of the egg's first meiotic division and cytoplasmic maturation, ovulation and formation of the corpus luteum.
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