Expression of ovarian prolactin receptor in relation to hormonal changes during induction of ovulation in the rat

The prolactin receptor: A cross-species comparison of gene structure, transcriptional regulation, tissue-specificity, and genetic variation

The conserved and multifaceted functions of prolactin (PRL) are coordinated through varied distribution and expression of its cell-surface receptor (PRLR) across a range of tissues and physiological states. The resultant heterogeneous expression of PRLR mRNA and protein across different organs and cell types supports a wide range of PRL-regulated processes including reproduction, lactation, development, and homeostasis. Genetic variation within the PRLR gene also accounts for several phenotypes impacting agricultural production and human pathology. The goal of this review is to highlight the many elements that control differential expression of the PRLR across tissues, and the various phenotypes that exist across species due to variation in the PRLR gene.

The progesterone and estrogen modify the uterine prolactin and prolactin receptor expression of hyperprolactinemic mice

The aim of this study was to evaluate the effects of metoclopramide-induced hyperprolactinemia on the prolactin (PRL) and PRL receptor's expression in the uterus of mice. For this purpose, 49 Swiss mice were divided into the following groups: GrSS (non-ovariectomized mice given vehicle); GrMET (non-ovariectomized mice treated with metoclopramide); OvSS (ovariectomized mice given vehicle); OvMET (ovariectomized mice treated with metoclopramide); OvMET+17βE (ovariectomized mice treated with metoclopramide and 17β estradiol); OvMET+MP (ovariectomized mice treated with metoclopramide and micronized progesterone); OvMET+17βE+MP (ovariectomized mice treated with metoclopramide and a solution of 17β estradiol and micronized progesterone). Immunohistochemical analyzes were evaluated semi-quantitatively. Our results showed that GrMET, OvMET+MP, and OvMET+17βE+MP presented strong PRL expression. OvMET and OvMET+17βE presented mild reaction, while GrSS and OvSS presented weak reaction. Concerning PRL receptor, OvMET+MP and OvMET+17βE+MP showed strong reaction; GrMET, OvSS, and OvMET+17βE showed mild reaction; and GrSS and OvMET showed weak reaction. These findings suggest that progesterone alone or in combination with estrogen may increase the expression of uterine PRL and PRL receptor.

Metoclopramide-induced hyperprolactinemia effects on the pituitary and uterine prolactin receptor expression

In this work we have evaluated the gene expression profile of prolactin and prolactin receptor in the pituitary and the uterus of female mice with metoclopramide-induced hyperprolactinemia treated with estrogen and/or progesterone. For this purpose, 49 Swiss female mice were allocated to seven groups.

INTERVENTIONS

50-day treatment with metoclopramide, progesterone and estrogen. Our results showed that in the pituitary, metoclopramide-induced hyperprolactinemia increased prolactin expression. In the castrated animals, progesterone, with or without estrogen, produced an increase in prolactin. Pituitary prolactin receptor and the estrogen and progesterone treatment were responsible for the rise in PRLR-S2. In the uterus, no differences in prolactin expression were found between the different study groups. PRLR-S1 had its expression reduced in all castrated animals as against the castrated group treated with vehicle. In the noncastrated animals, PRLR-S2 rose in the metoclopramide-treated group, and, in the castrated animals, its expression diminished in all groups in relation to the vehicle-treated castrated controls. An increase in PRLR-S3 was found in the oophorectomized animals treated with a combination of estrogen and progesterone. PRLR-L rose in the oophorectomized animals treated with progesterone in isolation or in association with estrogen. These findings suggest that metoclopramide associated to progesterone or estrogen may determine an increase in pituitary prolactin and PRLR-S2 expression. The estrogen-progesterone may enhance the expression of PRLR-S3 and PRLR-L isoform of prolactin receptor.

Dexamethasone enhances fertility and preovulatory serum prolactin levels in eCG/hCG primed immature rats

Glucocorticoids have heterogeneous effects on reproductive function. We used a gonadotropin-primed, immature rat model to study the influence of dexamethasone (1 mg/kg), given during the latter stages of follicular development, on litter size, the number of oocytes released, and pituitary hormone levels. Dexamethasone-treated females released a larger number of oocytes at ovulation and gave birth to larger litters indicating the oocytes were viable. Survival to weaning age was not affected but average weight at weaning was lower for pups born to DEX-treated females. Serum FSH and LH were assayed at 12, 24 and 48 h following eCG and did not differ between dexamethasone-treated and control animals, but prolactin showed a prolonged pattern of elevation in DEX-treated females. Prolactin, which normally exhibits an elevation on proestrous, may modulate follicular development. Dexamethasone enhances fertility and fecundity possible through an effect of prolactin on follicle development, or by other direct effects on the ovary. These results may improve our understanding of the usefulness of DEX in assisted reproductive therapies for women.

Cloning and functional characterization of allelic variation in the porcine prolactin receptor

Prolactin (PRL) regulates various functions in pigs including reproduction, mammary development and lactation. We used 5'-rapid amplification of cDNA ends (5'-RACE) to clone three full-length alleles of the porcine PRL receptor (pPRLR) from Landrace (alleles LR2 and LR4) and Yucatan miniature (MP) pigs, corresponding to the A and B alleles previously reported to be associated with reproductive traits. When expressed in Chinese hamster ovary (CHO-K1) cells, all three pPRLRs transduced differentiation signals to a beta-casein promoter with the same effectiveness, where human growth hormone (hGH) and porcine PRL (pPRL) were more effective ligands than ovine PRL (oPRL). The pPRLR had a lower binding affinity for oPRL than pPRL while binding affinity for hGH was not different between the three pPRLR variants. The pPRLRs primarily localized to the cytoplasm with perinuclear concentration. In conclusion, we have cloned three allelic variants of the pPRLR and have functionally characterized these as different from the hPRLR. However, our data do not support the proposal that allelic variation of the pPRLR confers functional differences in vivo.

Morphometric and hormonal changes during the chimpanzee menstrual cycle

BACKGROUND

Sex steroids affect many peripheral tissue sites in female mammals. Receptors for these hormones have been found in skin, fat, and bone. In women, these tissues can show morphological changes during the menstrual cycle that may be directly related to steroid secretion.

METHODS

The present study was done on chimpanzees to document morphometric markers associated with these tissues (anogenital swelling volume, skin fold thickness as indicator of subcutaneous fat, bony diameters of mandible, wrist, and elbow) and to compare them with cyclic patterns of estradiol, progesterone, testosterone, gonadotropins, and prolactin.

RESULTS

Swelling volume changed significantly over the menstrual cycle. All other morphometric parameters showed variation without statistical significance. Skin folds were thickest during the luteal phase. Bony diameters displayed similar but less distinctive changes. Testosterone correlated positively with diameter sites, inversely with subcutaneous fat. No relationships with either estradiol or progesterone were found. We assume that subcutaneous fat and morphometric bone parameters exhibit cycle-dependent changes that may be caused by changes in steroid secretion.

Impact of social environment on female chimpanzee reproductive cycles

The socio-sexual environment of a female is known to affect ovarian function. Increased male contact can enhance menstrual cycle regularity. Conversely, social deprivation constitutes a form of stress that often alters cyclicity and the secretion of reproductive hormones. The present study was carried out on captive female chimpanzees to examine possible interactions among housing conditions, menstrual cycle length, morphological changes in secondary sexual character expression and endocrine release patterns related to follicular and luteal function. Animals were housed over a period of 2 years either with a male conspecific or singly. Blood samples were collected over three cycles, and anogenital swelling changes registered to define menstrual cycle phases. Fecal sampling techniques were used to monitor cortisol as a measure of stress-load. Male presence seemed to affect female cyclicity. Females housed with a male had shorter and more regular cycles than singly housed females. Prolactin, gonadotropins and estradiol levels were generally higher in paired females during specific cycle phases. Group variation was not always significant. No differences were found in progesterone. Sexually cohabited females tended to have lower fecal cortisol metabolites immediately before and after maximum tumescence. We suggest that the close behavioral, physical and olfactory contact with a male conspecific can act as a sort of zeitgeber to modulate ovarian function by stabilizing the female cycle and, perhaps, enhancing folliculogenesis and ovulation.

Upregulation of hepatic prolactin receptor gene expression by 17beta-estradiol following trauma-hemorrhage

Although studies show protective effects of 17beta-estradiol (E2) or prolactin (PRL) treatment in male rats after trauma-hemorrhage (TH), the mechanism of the salutary effects of these agents remains unknown. Because E2 modulates PRL receptor (PRL-R) expression in the liver, we examined whether E2 treatment after T-H has any effects on hepatic PLR-R gene expression. Male Sprague-Dawley rats were subjected to trauma (i.e., 5-cm midline laparotomy) and hemorrhage (35-40 mmHg for 90 min) followed by fluid resuscitation (Ringer lactate) or sham operation and then treated with E2 (50 microg/kg body wt sc) or vehicle immediately before resuscitation. Liver samples were collected at 3 h thereafter, and PRL-R mRNA expression was determined by PCR. Liver expression of PRL-R short-form gene was unaffected by T-H, whereas that of the long-form gene was suppressed. Treatment of T-H rats with E2 significantly increased PRL-R short-form gene expression and normalized PRL-R long-form gene expression to sham levels. In the isolated hepatocytes, PRL-R short-form gene expression was predominant compared with the long-form gene. In contrast, only the short form was detected in Kupffer cells. In vitro treatment by E2 demonstrated an increase in the PRL-R long-form gene in hepatocytes, but E2 had no effect on PRL-R short-form gene expression in either the Kupffer cells or hepatocytes. Thus E2 treatment after T-H in males appears to directly upregulate PRL-R long-form gene expression in hepatocytes. However, the upregulation of the PRL-R short form might involve the interaction of multiple cell types in the liver.