Follicular Phase Length Research Articles

Measurement of Serum Steroid and Gonadotropin Levels and Uterine and Ovarian Variables throughout 4 Day and 5 Day Estrous Cycles in the Rat1

The present study was undertaken to characterize hormonal and morphological events in 4 day and 5 day rat cycles, in order to test 3 different theories concerning the etiological factors altering follicular phase length in mammals. Three rats were killed at each 2 h interval throughout each cycle type. In addition to organ weight measurements, serum levels of estradiol, progesterone, 20α-hydroxypreg-4-en-3-one, LH, FSH and prolactin were assessed in terminal samples. The beginning of uterine intraluminal fluid accumulation coincided with the decline in progesterone levels seen during diestrus, rather than with the rise in estrogen and was delayed 12 h in the 5 day cycle from the time of last estrus. The retention of this fluid during the evening of proestrus was 6 h longer in the 4 day cycling rat. Ovulation occurred earlier in the 5 day cycling rats than in those with a 4 day cycle. No significant differences in the gonadotropins or 20α-hydroxypreg-4-en-3-one were seen when comparing the 2 types of cycles. Estradiol rose during the night of diestrus I (the same time in the cycle) and was identical in both cycle types. Progesterone was not released on proestrus prior to the LH surge in either type of cycle. However, we did find that progesterone values were higher for a longer period of time throughout diestrus I in 5 day cycles. These data have led us to conclude that the 5 day cycle is due to a prolonged progesterone secretion during the metestrous and diestrous stages of the cycle.

The measurement of total plasma oestrogens during the follicular phase of the mare's oestrous cycle

The measurement of total plasma oestrogens (conjugated and unconjugated) gives 100 times higher levels than the specific measurement of 17β oestradiol. Such high levels are easy to measure and give a good picture of the follicular activity of the mare. A correlation was found between length of follicular phase of the cycle and oestrogen levels at the time of luteolysis (r = 0.47) or preovulatory oestrogen levels (r = +0.40).

Effects of stress on pregnancy in the rat.

Although stress or injections of ACTH or adrenal glucocorticoids have been associated with impaired reproductive performance in many species, the mechanisms by which these treatments affect reproduction remains obscure. Previous studies have indicated that stress may influence several stages of the normal reproductive process. Rowell (1970) reported increased follicular phase length and longer menstrual cycles following stress in baboons, and Hagino, Watanabe & Goldzieher (1969) found that stress, ACTH or glucocorticoids could block PMSG-induced ovulation in rats. Adrenocortical activation in the pre-implantation phase has also been reported to inhibit fertility. Bruce (1967) showed that the stress of a strange male introduced to mated female mice resulted in a return to oestrus without apparent luteal function and Yang, Yang & Lin (1969) found that although ACTH injection in the preimplantation phase did not alter the time interval required for ova to enter the uterus in rats, the number of implantations was

Change of Ovarian Function with Age

It is recognized statistically and clinically that the lowering of female fertility appears with age. During the climacteric, there is frequent to happen ovarian dysfunction, such as menstrual disorders or dysfunctional uterine bleeding, and the climacteric symptoms as somatic and psychic changes. These clinical changes suggest the lowering of ovarian function according to aging. However, from the aspects of urinary estrogen level, the strinkig decrease of the level is not observed before menopause. In postmenopausal women, it is low value, as general, but the higher levels are revealed in some cases. In any event, very low level as in childhood is not observed.From the recording of 18,213 menstrual cycles, it is observed that the length of cycle shortens with age. Basal temperature records of 3,000 ovulatory cycles shows that the average length of follicular phase shortens with age, although that of luteal phase does not change in women of over 20 years old. So it is clear that the shortening of menstrual cycle is a result of shortening of follicular phase. The shortening of period and decrease of flow are also observed in women of over 35 years old, and the increase of inadequate luteal phase or anovulatory cycle especially in women of over 40 years old.Lowering of ovarian function with age does not mean only the decrease of estrogen secretion, but irregularity of ovarian cycle function that induces umblance of estrogen and progesterone secretion. The fact that the endometrial hyperplasia induced by prolonged or profuse estrogen action frequently takes place in climacteric women supports the abovementioned opinion.Urinary total gonadotrophins increase in some cases of menopausal women, and rise remarkably in postmenopausal women. Follicle stimulating hormone is within normal value or a little higher before menopause, and rises usually in postmenopausal women. Then, in more than five years after menopause, FSH tends to return to normal range. LH increases to ovulatory level in postmenopausal women. Urinary 17KS value increases during menopause.With age, ovarian size becomes smaller, and following histological changes appear : appearance of germinal inclusion cyst or corpus albicans cyst, disappearance of corpus luteum, decrease of atretic follicle, disappearance of graafian follicle, decrease of a number of a internal theca cell and interstitial cell, accumulation of Sudan IV strain in ovarian cortex, and increase of Sudan IV strain in wand of ovarian vessels. From these phenomenon, it is supposed that structual ovarian atrophy begins between 35 and 40 years old. Especially blood vessels in ovary change remarkably after 35 years old. So, the change of ovarian vessel is suggested to play an important role to lowering of ovarian function.