The EflFects of Gonadal Steroids on Plasma Gonadotropins and Prolactin in the Rat1

Kalra, Pushpa S.; Fawcett, C. P.; Krulich, L.; Cann, S. M. Mc

doi:10.1210/endo-92-4-1256

Cited by 197 publications

(85 citation statements)

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“…Kalra et al, 1973), there was no correlation between the prolactin concentration and the oestradiol17f concentration in the same sample of blood in normal females, females bearing mammary carcinomata, or females with mammary carcinomata after ovariectomy and treatment with oestrogen. This is not unexpected since the release of prolactin by oestrogen does not commence until 4-8 h after administration of the latter (unpublished observations) and thus prolactin levels are probably determined by the oestrogen concentration which prevailed many hours earlier.…”

Section: Discussionmentioning

confidence: 81%

Oestradiol-17β and prolactin levels in rat peripheral plasma

Hawkins¹,

Freedman²,

Marshall³

et al. 1975

Br J Cancer

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Summary.-Radioimmunoassay methods for the determination of oestradiol-17p and prolactin have been examined for their reliability and applied to the measurement of hormone concentrations in the plasmas from male and female rats. Prolactin was detectable in all samples (>7 ng RP-1 ng/ml) but the concentration of oestradiol-17p was below the sensitivity of the method (>0*10 ng /lOOml) in ovariectomized females. Plasma oestradiol-17p concentration rose gradrfally from metoestrus to proestrus and fell to barely detectable levels in oestrus. Plasma prolactin concentration was very variable even for rats in the same stage of the oestrous cycle but values were minimal in the afternoon of diestrus and a surge in secretion occurred in the afternoon of proestrus. In addition to the stage of the oestrous cycle, the prolactin concentration was influenced by mode of blood collection, degree of haemolysis and choice of serum or plasma. There was no correlation between the concentration of prolactin and that of oestradiol-17P in the same sample of plasma.IN THE RAT, the growth of experimental mammary tumours induced by the administration of the carcinogen 7,12-dimethylbenzanthracene (DMBA) has been reported to be influenced by both oestrogen (Dao and Sinha, 1972), and prolactin (Pearson, 1969). As a preliminary to an investigation of the role of these hormones in tumour growth, we have set up methods for their measurement by radioimmunoassay. The reliability of each method has been examined and the basal levels of each hormone have been measured at various stages during the oestrous cycle, in ovariectomized animals and in males. Although the fluctuations in plasma oestradiol-17/3 (Hori, Ide and Miyake, 1968;Yoshinaga, Hawkins and Stocker, 1969;Brown-Grant, Exley and Naftolin, 1970; Shaikh, 1971;Dupon and Kim, 1973), and plasma prolactin (Kwa and Verhofstad 1967; Niswender et al., 1968;Gay, Midgeley and Niswender, 1970;Amenomori, Chen and Meites, 1970;Neill and Reichert, 1971;Neill, 1972) during the oestrous cycle have been reported previously, the results of simultaneous measurements of both hormones in individual rats have not to our knowledge been published. MATERIALS AND METHODSAnimals.-Randomly bred SpragueDawley rats were maintained on a lighting; darkness schedule of 12 h L: 12 h D, with the lights switched on at 0700 hours. Vaginal smears were taken daily by lavage and the rats were followed for at least 2 cycles. Only rats with regular 4-day cycles were used and stage in the cycle was defined as previously described (Yoshinaga et al., 1969).Blood was withdrawn into a hepariniZed syringe from the abdominal aorta under ether anaesthesia except when otherwise stated. Blood samples were cooled in ice and the plasma was separated by centrifugation at 4 TC at approximately 1300 g. In one experiment, serum was prepared by the collection of non-heparinized blood, allowing the blood to clot for at least 2 h at 4 TC and centrifugation. Haemolysed plasma was prepared by the addition of water to heparinized blood

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Section: Discussionmentioning

confidence: 81%

Oestradiol-17β and prolactin levels in rat peripheral plasma

Hawkins¹,

Freedman²,

Marshall³

et al. 1975

Br J Cancer

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“…First, surgery can affect pain thresholds [93,173] and sensitivity to analgesics. Second, gonadectomy disrupts the normal feedback loop that sex steroids exert on the anterior pituitary and hypothalamus, leaving both males and females in a prolonged state of elevated (e.g., gonadotropin-releasing hormone (GnRH), leuteinizing hormone) or depressed (e.g., prolactin) circulating hormones [1,53,95,220]. The likelihood of unintended consequences due to altered hypothalamic/pituitary hormone secretion can be addressed by administering low (maintenance) doses of estradiol or testosterone rather than using gonadectomized animals with no hormone replacement.…”

Section: Hormone Manipulations: Animal Studiesmentioning

confidence: 99%

Section: Hormone Manipulations: Animal Studiesmentioning

confidence: 99%

“…The likelihood of unintended consequences due to altered hypothalamic/pituitary hormone secretion can be addressed by administering low (maintenance) doses of estradiol or testosterone rather than using gonadectomized animals with no hormone replacement. In the case of the female rat, daily s.c. injections of 1 μg estradiol benzoate are sufficient to reduce leuteinizing hormone and to elevate prolactin to diestrous levels without inducing receptive behavior [1,95].Although there are "chemical castration" alternatives to gonadectomy, these have drawbacks and have not been fully characterized in terms of their possible effects on pain/analgesia. For example, continuous GnRH can be used to shut down the hypothalamo-pituitary-gonadal axis in both males and females.…”

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confidence: 99%

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Studying sex and gender differences in pain and analgesia: A consensus report

Greenspan

Craft

LeResche

et al. 2007

Pain

871

633

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In September 2006, members of the Sex, Gender and Pain Special Interest Group of the International Association for the Study of Pain met to discuss the following: (1) what is known about sex and gender differences in pain and analgesia; (2) what are the "best practice" guidelines for pain research with respect to sex and gender; and (3) what are the crucial questions to address in the near future? The resulting consensus presented herein includes input from basic science, clinical and psychosocial pain researchers, as well as from recognized experts in sexual differentiation and reproductive endocrinology. We intend this document to serve as a utilitarian and thought-provoking guide for future research on sex and gender differences in pain and analgesia, both for those currently working in this field as well as those still wondering, "Do I really need to study females?" Keywords Sex differences; Gonadal hormones; Estrogens The case for studying sex and gender differences in pain and analgesiaThe pain field has moved from debating whether sex differences in pain exist to recognizing the importance of these differences. Attention is now directed toward understanding (1) what conditions lead to the expression of sex and gender differences in pain experience and reactivity, (2) what mechanisms underlie these differences, and (3) how these differences can inform clinical management of pain.As noted in a recent review, at least 79% of animal studies published in Pain over the preceding 10 years included male subjects only, with a mere 8% of studies on females only, and another 4% explicitly designed to test for sex differences (the rest did not specify) [142]. Given the substantially greater prevalence of many clinical pain conditions in women vs. men [20,199], and growing evidence for sex differences in sensitivity to experimental pain and to analgesics [21,41,213], we recommend that all pain researchers consider testing their hypotheses in both sexes, or if restricted by practical considerations, only in females. It is invalid to assume that data obtained in male subjects will generalize to females, and the best non-human model of the modal human pain sufferer -a woman -is a female animal. If only males are examined in a given study, it is important that a rationale for exclusion of females be provided and that the potential limitation in generalizability of the findings be addressed in the discussion, particularly when examining a pain phenomenon that occurs with greater prevalence or severity in females. In both preclinical and clinical studies, a comparison of both sexes will further our understanding of individual differences in sensitivity to pain and analgesia, thus improving our ability to treat and prevent pain in all people. General considerationsTwo issues of terminology are important. First, the term "sex" refers to biologically based differences, while the term "gender" refers to socially based phenomena. Although biological sex exerts a major influence on one's gender identity, sex and gender a...

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“…It has long been shown that estrogens play an important role in the control of prolactin (PRL) secretion in mammals and are able to stimulate circulating PRL concentrations (Chen and Meites, 1970;Kalra et al, 1973;Shin et al, 1974). However, their mechanisms of action are still debated.…”

Section: Introductionmentioning

confidence: 99%

Absence of direct regulation of prolactin cells by estradiol-17β in rainbow trout (Oncorhynchus mykiss)

Goff

Salbert

Prunet

et al. 1992

Molecular and Cellular Endocrinology

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SummaryThe effects of estradiol-17/3 (E,) implants on plasma prolactin (PRL) concentrations, pituitary PRL content and pituitary PRL mRNA levels were examined in rainbow trout (Oncorhynchus mykiss). Intact immature fish treated with 1 mg estradiol-17/? did not show significant changes in both PRL mRNA levels and pituitary PRL content after 3 days of treatment. In a similar experiment, no changes were observed in plasma PRL levels followed during 7 days. Similarly, lack of estradiol-17/3 effect on plasma PRL levels and on final PRL pituitary content was observed in ovariectomized female rainbow trout treated during 48 days with 25 mg estradiol-17P and in mature male fish over a 3-week treatment period. Localization of estradiol receptor (ER) mRNAs in the pituitary was carried out by Northern blot analysis using a full-length rainbow trout estrogen receptor (rtER) cDNA as a probe. The rostra1 pars distalis of the pituitary which contained mostly PRL cells showed the lower amount of rtER mRNA when compared to other parts of the pituitary. Moreover, two mRNAs of different size (3.5 and 1.4 kb) were detected in different parts of the pituitary. Further hybridization experiments using probes containing part of the rtER cDNA (E domain or C and D domains) indicated that the small-sized mRNA (1.4 kb) probably encodes a truncated ER protein lacking hormone binding domain or an ER-related protein. Thus, only the 3.56 kb mRNA appeared to be involved in the regulation of pituitary function by estradiol. In situ hybridization analysis allowed a more precise localization of this rtER mRNA in the pituitary. No labeling was discernible over PRL cells whereas other parts of the pituitary were labeled. Grain counting corroborated this localization. These results indicate that (1) in vivo estradiol-17P treatment did not modify PRL cell activity in rainbow trout, (2) PRL secretion, in this fish species, is not directly regulated by estradiol.

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The EflFects of Gonadal Steroids on Plasma Gonadotropins and Prolactin in the Rat1

Cited by 197 publications

References 0 publications

Oestradiol-17β and prolactin levels in rat peripheral plasma

Oestradiol-17β and prolactin levels in rat peripheral plasma

Studying sex and gender differences in pain and analgesia: A consensus report

Absence of direct regulation of prolactin cells by estradiol-17β in rainbow trout (Oncorhynchus mykiss)

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