Peripheral Plasma Oestradiol and Luteinizing Hormone Concentrations During the Oestrous Cycle of the Rat

Estrogen deficiency causes central leptin insensitivity and increased hypothalamic neuropeptide Y

“…In contrast, treating sham-operated rats with estradiol had no effect on body weight, body fat or energy balance compared to sham rats treated with placebo pellets. Plasma estradiol levels in ovariectomized animals were negligible (0.06 AE 0.01 pg=ml), while estrogen treatment of ovariectomized and sham rats increased circulating estradiol concentrations to a level within the range reported in the literature in intact rats 37 (ovex estrogen-treated, 17 AE 6 pg=ml, sham estrogen-treated, 20 AE 5 pg=ml; sham, 2 pg=ml (diestrus) to 30 pg=ml (proestrus)).…”

A Priming Effect of Luteinizing Hormone Releasing Factor on the Anterior Pituitary Gland in the Female Rat

“…The significantly greater response at pro-oestrus compared with those on the other days of the cycle appears to be dependent mainly upon the rise in plasma con¬ centrations of oestradiol-11 ß which reaches a peak on the morning of pro-oestrus (Brown-Grant, Exley & Naftolin, 1970;Shaikh, 1971) (Motta, Fraschini & Martini, 1969;Ojeda & Ramirez, 1969). Thus it seems likely that LH-RF itself sensitizes the gonadotrophs.…”

On Circulating Sex Steroids During the Estrous Cycle and the Early Pseudopregnancy in the Rat with Special Reference to its Luteal Activation

“…Measurements of radioactivity Counting and data processing were carried out as previously reported (Horikoshi and Wiest, 1971 assessed directly by the estrogen assays in the ovarian venous blood (Hori et al, 1968 ;Yoshinaga et al, 1969 ;Shaikh, 1971) or in the peripheral blood (Brown-Grant et al, 1970), though these data have been mainly compiled only in the stages of diestrus and proestrus . As seen in Figure 1-a, our data clearly indicate that the circulating E-2 shows only one rise spreading from 1600 of Day D to 1400 of Day P throughout the estrous cycle.…”

“…This picture is good accord not only with the change of uterine weight including the luminal fluid, but also with the secretory pattern of estrogen reported by the previous workers. Since the ovulatory surge of LH release has been proved to occur from 1600 to 2000 of Day P (Monroe et al, 1968;Goldman et al, 1969 ;Gay et al, 1970 ;Brown-Grant et al, 1970;Barraclough et al, 1971), the decline of the increased secretion of E-2 as indicated by the abrupt drop in E-2 level, seems to start before the LH surge. Our data are compatible with a hypothesis that estrogen acts as a trigger for the ovulatory release of LH (Everett, 1948 ;Miyake, 1968 ;Kobayashi et al, 1969).…”