Follicle-Stimulating Hormone-Releasing Factor (Fsh-Rf) and Luteinizing Hormone-Releasing Factor (Lh-Rf) in Rat Hypothalamic Extract

Abstract

SYNOPSISHypothalamic tissues of female rats were extracted with 1.M acetic acid. The acidic extract was lyophilized and subjected to gel filtration on Sephadex column and assayed for follicle-stimulating hormone-releasing factor (FSH-RF) activity and luteinizing hormone-releasing factor (LH-RF) activity by estimating FSH and LH using the organ culture method of rat anterior pituitaries. FSH activity was measured by the method of Steelman-Pohley, and LH activity by the method of Parlow. Gel filtration on a short column of Sephadex G-25 in 0.1M pyridine acetate provided a single fraction which showed significant FSH-RF and LH-RF activity. Each activity showed a doserelated increase. Application of a long column of Sephadex G-25 in 0.05M pyridine acetate brought about separation of a peak for FSH-RF activity from that for LH-RF activity. The former activity was eluted from the column just before the appearance of the latter. These results indicated that the secretion of FSH and LH from the rat anterior pituitary was regulated by the specific hypothalamic FSH-RF and LH-RF, respectively.Many experiments have convincingly demonstrated the presence of gonadotropinreleasing factor (GRF) in the rat hypothalamus. Injection of acidic extracts of the hypothalamus induced depletion of ovarian ascorbic acid in immature rats made pseudopregnant by pretreatment with gonadotropin (McCann et al., 1960) and elevated the LH level in plasma of normal or ovariectomized, estrogen and progesterone-treated rats . The extracts also induced ovulation in pentobarbital blocked proestrous rats when infused directly into the pituitary (Nikitovitch-Winer, 1962). We have recently reported that the acidic extracts added to the culture medium stimulate the release of LH by the cultivated pituitaries (Kobayashi et al. 1966). These results indicate the presence of luteinizing hormone-releasing factor (LHRF) in the rat hypothalamus. The existence of follicle-stimulating hormonereleasing factor (FSH-RF) in the rat hypo thalamus has been demonstrated by the fact that injection of the acidic extracts produced a rise in FSH level in plasma of ovariectomized, estrogen and progesterone-treated rats (Igarashi and McCann, 1964) and addition of the extracts stimulated FSH release by the cultivated pituitary (Mittler and Meites, 1964).

The Effects of Hypothalamic Lesions on the Release of Gonadotropins and Prolactin in Response to Estrogen and Progesterone Treatment in Female Rats

“…Although FSH-releasing factor (FRF) was separated from LRF in tests employing bioassay of gonadotropins (17)(18)(19)(20), recent work utilizing immunoassay of gonadotropins has failed to demonstrate a separate FRF during the isolation of LRF (21,22). Furthermore, natural LRF and the synthetic decapeptide have intrinsic although lesser FSH-releasing activity (Fawcett,unpublished data,22,23).…”

Stimulation of Lh Secretion in Constant Estrous Rats Under Constant Illumination by Rat Hypothalamic Extract

“…after injection, and it was followed by both a depletion of pituitary LH and a coincident rise of plasma LH. In our previous experiments (Kobayashi et al, 1967) the anterior pituitary glands were cultivated with addition of LH-RF preparation partially purified on a column of Sephadex. After 2days cultivation with the LH-RF, LH activities of the culture media and the glands were separately estimated by the ovarian ascorbic acid depletion method.…”