Estradiol Potentiates But Is Not Essential for Prolactin-Induced Suppression of Luteinizing Hormone Pulses in Female Rats

Abstract

Hyperprolactinemia causes infertility by suppressing gonadotropin-releasing hormone (GnRH) and luteinizing hormone (LH) secretion. Because effects of prolactin (PRL) on the hypothalamus usually require estradiol (E2), we investigated the role of E2 in PRL-induced suppression of LH pulses. Ovariectomized (OVX) rats treated with oil or E2 (OVX + E2) received a subcutaneous injection of ovine PRL (oPRL) 30 minutes before serial measurement of LH in the tail blood by enzyme-linked immunosorbent assay. E2 reduced pulsatile LH secretion. oPRL at 1.5 mg/kg further reduced LH pulse frequency in OVX + E2 but had no effect in OVX rats. The higher dose of 6-mg/kg oPRL decreased LH pulse frequency in both OVX and OVX + E2 rats, whereas pulse amplitude and mean LH levels were lowered only in OVX + E2 rats. Kisspeptin immunoreactivity and Kiss1 messenger ribonucleic acid (mRNA) levels were decreased in the arcuate nucleus (ARC) of OVX + E2 rats. oPRL decreased both kisspeptin peptide and gene expression in the ARC of OVX rats but did not alter the already low levels in OVX + E2 rats. In the anteroventral periventricular nucleus, oPRL did not change kisspeptin immunoreactivity and, paradoxically, increased Kiss1 mRNA only in OVX + E2 rats. Moreover, oPRL effectively reduced Gnrh expression regardless of E2 treatment. In this study we used tail-tip blood sampling to determine the acute effect of PRL on LH pulsatility in female rats. Our findings characterize the role of E2 in the PRL modulation of hypothalamic components of the gonadal axis and LH release, demonstrating that E2 potentiates but is not essential for the suppression of pulsatile LH secretion caused by hyperprolactinemia.

Growth hormone receptor in dopaminergic neurones regulates stress‐induced prolactin release in male mice

“…[45][46][47] Additionally, prolactin regulates reproduction and fertility. 23,48,49 Our findings suggest that GHR deletion in DAT-or TH-expressing cells did not affect fertility and pup survival. However, because we did not per- SCH regulates circadian rhythms, and PMv neurones are known to mediate the effects of leptin on reproduction [50][51][52] and regulate intermale aggression.…”

“…Besides the effect of prolactin with respect to stimulating milk production, prolactin is necessary for postpartum maternal nursing behaviour 45‐47 . Additionally, prolactin regulates reproduction and fertility 23,48,49 . Our findings suggest that GHR deletion in DAT‐ or TH‐expressing cells did not affect fertility and pup survival.…”

“…Plasma prolactin levels were determined using ultrasensitive prolactin enzyme‐linked immunosorbent assay. The assay was performed as previously described, 23 with the exception that mouse prolactin (AFP‐6476C; NHPP) was used as reference preparation. Briefly, a 96‐well high‐binding plate (9018; Corning Inc., Corning, NY, USA) was coated with 50 μL of guinea pig anti‐rat prolactin antibody (AFP65191; NIDDK‐NHPP; ; dilution 1:1500) overnight at 4°C.…”

“…Plasma prolactin levels were determined using ultrasensitive prolactin enzyme-linked immunosorbent assay. The assay was performed as previously described, 23 with the exception that mouse prolactin…”

The Association Between Prolactin and Metabolic Parameters in PCOS Women: A Retrospective Analysis

“…We found significant negative correlation between serum PRL and LH and LH/FSH. Under certain physiological and pathological conditions, high serum PRL above the normal range can directly inhibit the synthesis and release of gonadotropin releasing hormone (GnRH) from the hypothalamus (44) and reduce the secretion of GnRH to the portal vein (45), and high serum PRL also can suppress kisspeptin neurons in the arcuate nucleus (46), resulting in the suppressing the frequency and amplitude of FSH and LH pulses (47,48). Whether the significant negative relationship between serum PRL and LH or LH/FSH found in our study is an indication that serum PRL in normal range would suppress the secretion of gonadotropin is still not clear.…”