Dynamic Studies of Growth Hormone and Prolactin Secretion in the Female Rat

Saunders, Alex M.; Terry, L. Cass; Audet, Judy; Brazeau, Paul; Martin, Joseph B.

doi:10.1159/000122525

Cited by 152 publications

(73 citation statements)

References 6 publications

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“…Suckling of the nipple by the neonate or milking is one of the most important factors, providing a powerful prolactin stimulus, involved in maintaining a prolonged state of hyperprolactinaemia (Grattan 2002). Investigating a temporal course of prolactin and GH secretion in the individual ewes, our data show a high similarity to those obtained on lactating rats (Saunders et al 1976, Riskind et al 1984, Wehrenberg & Gaillard 1989 or cows (Negrao & Marnet 2002). It has been proposed that suckling or milking works by decreasing prolactin-inhibiting factor (DA) from the hypothalamus, and thereby increasing prolactin levels.…”

Section: Discussionsupporting

confidence: 64%

Identification of salsolinol in the mediobasal hypothalamus of lactating ewes and its relation to suckling-induced prolactin and GH release

Misztal

Górski²,

Tomaszewska-Zaremba³

et al. 2008

Journal of Endocrinology

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The push-pull perfusions of the infundibular nucleus-median eminence (IN/ME) were made in lactating ewes (nZ7) twice, to identify dopamine (DA)-derived salsolinol and the changes in its extracellular concentration in response to suckling. The perfusate collecting period in every ewe consisted of control non-suckling period, 1000-1230 h (five perfusates), and suckling period, 1230-1500 h (next five perfusates). Simultaneously, blood samples were collected from 1000 to 1500 h at 10-min intervals. The perfusate concentrations of salsolinol and DA were measured by HPLC, and plasma prolactin and GH concentrations were assayed by the RIA. Mean concentrations of salsolinol in perfusates collected from the anterior and posterior parts of the IN/ME (according to post-mortem localization of a perfusion site) increased significantly (P!0 . 05 and P!0 . 001 respectively) during the suckling period, when compared with those noted during the non-suckling period. While no DA was found in the anterior part, only vestigial amounts of DA were found in a few perfusates collected from the posterior part. Salsolinol was not detected in the IN/ME of ewes 10 weeks after weaning (seasonal anoestrus). Mean plasma prolactin and GH concentrations during suckling were significantly (P!0 . 001) higher than those noted during the non-suckling period. In conclusion, our current study reveals that salsolinol is present in the IN/ME of lactating ewes and that its extracellular concentration increases during suckling. Moreover, it supports the role of salsolinol as a neurotransmitter involved in the regulatory process of prolactin secretion at least during lactation.

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Section: Discussionsupporting

confidence: 64%

Identification of salsolinol in the mediobasal hypothalamus of lactating ewes and its relation to suckling-induced prolactin and GH release

Misztal

Górski²,

Tomaszewska-Zaremba³

et al. 2008

Journal of Endocrinology

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“…Many studies have indicated that high-amplitude GH pulses in rats and humans, mean blood GH secretion in rats, and integrated GH values in humans diminish during aging (33)(34)(35)(36)(37)(38)(39)(40)(41). The mechanisms involved are unknown but may be due to alterations in the release of GRF and/or SRIF from the hypothalamus.…”

Section: Discussionmentioning

confidence: 99%

Levels of human and rat hypothalamic growth hormone-releasing factor as determined by specific radioimmunoassay systems.

Audhya¹,

Manzione²,

Nakane³

et al. 1985

Proc. Natl. Acad. Sci. U.S.A.

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Polyclonal antibodies to synthetic human pancreatic growth hormone-releasing factor )NH2] and rat hypothalamic growth hormone-releasing factor [rhGRF(1-43)OHJ were produced in rabbits by injecting these weak immunogens, coupled to thyroglobulin and emulsified with complete Freund's adjuvant in the presence of activated charcoal, directly into the spleen. A subsequent booster in-jection by the conventional intramuscular route resulted in high-titer antibodies, which at a 1:20,000 dilution were used to develop highly sensitive and specific radioinmunoassays for these peptides. By using antibodies with an apparent K. of 3.3x 10-12 (human) and 7.7 x 10-11 (rat), the sensitivity of these assays in both human and rat was found to be <1 fmol. The antibody to hpGRF(1-44)NH2 is directed against the COOHterminal region of the molecule, as shown by its crossreactivity with various hpGRF analogues: 140% with hpGRF(30-44)NH2; 1%-2% with hpGRF(1-37)OH, hpGRF(140)OH, and hpGRF(1-40)NH2; and none with hpGRF(1-29)NH2. Serial dilutions of human and rat hypothalamic extracts demonstrated parallelism with the corresponding species-specific standard and 12,5-labeled tracer. There was no crossreactivity with other neuropeptides, gastrointestinal peptides, or hypothalamic extracts of other species. The hypothalamic content in fmol/mg (wet weight) of tissue was 3.6 ± 0.2 for the human and 11.1 ± 5.5 for the rat. Age-related changes in hypothalamic GRF content were present in rats, with a gradual increase from 2 to 16 weeks and a correlation between increasing body weight and GRF content. These radioimmunoassays winl serve as important tools for understanding the regulation of growth hormone secretion in both human and rat.Since 1959 (1), it has been known that the hypothalamus is involved in the control of growth hormone (GH) secretion. Experimental and clinical evidence has since indicated that the hypothalamus performs a dual function in the regulation of GH secretion from the anterior pituitary (2-4). Inhibition of GH release is accomplished by an inhibitory peptide, somatostatin (SRIF), which in 1972 was isolated from ovine hypothalami, purified, and characterized as a tetradecapeptide (5). In contrast, as suggested by physiological evidence (2-4) and GH-releasing activity in hypothalamic extracts (6-8), stimulation of GH release is accomplished by a stimulatory peptide, GH-releasing factor (GRF). Until 1982, howev-er, the isolation and characterization of GRF remained elusive. The difficulty in its characterization had been due to the minute quantities of the peptide in hypothalamic tissue, the large quantities of SRIF that interfere in the bioassay, and the fact that the methodology used for peptide sequencing and purification has only recently become available (9-12).The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact. 2970Many investigators have reported the presenc...

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“…This has been evidenced both in the adult male rat (Martin, RenaudBrazeau, 1976;Tannenbaum, Martin & Colle, 1976;Tannenbaum, Rorstad & Brazeau, 1979) and in the adult female rat (Saunders, Terry, Audet, Brazeau & Martin, 1976). It has been demonstrated moreover that the secretion is governed by an endogenous ultradian rhythm with major secretary episodes occurring at approximately 3-3 h intervals throughout a 24-h period in the adult male rat .…”

Section: Introductionmentioning

confidence: 94%

Relationship between the three‐hour‐period sleep‐wakefulness cycle and growth hormone secretion in the immature rat.

Kawakami¹,

Kimura²,

Tsai³

1984

The Journal of Physiology

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SUMMARY1. The temporal pattern of growth hormone (GH) secretion throughout a day and its correlation with the sleep-wakefulness cycle in the 29-31-day-old female rat were studied by serial blood sampling through an intracardiac cannula at 10-min intervals. Electroencephalograms (e.e.g.s) recorded continuously during blood sampling periods were scored into wakefulness and sleep, and the amount of sleep for every 10 min was plotted against the GH value as assessed by radio-immunoassay.2. By analysis of the power spectrum using the least-squares method, the time series of GH concentration was found to have a periodicity of approximately 3 0 h in any of the 6-h periods sampled, beginning at 12.00, 18.00, 00.00 and 06.00 h, and in either sex.3. The peak time which was estimated for the time series of GH concentrations was found to occur consistently around 02.00-03.00, 05.00-06.00, 08.00-09.00, 11.00-12.00, 14.00-15.00, 17.00-18.00, 20.00-21.00 and 23.00-24.00 h in either the male or the female rat.4. The cross-correlation analysis performed between the time series of the amount of sleep and the GH concentration, which were obtained for the 6-h period from 12.00 to 18.00 h, revealed a significant positive correlation between the GH level and the amount of sleep during the preceding 10 min.5. The time series of the amount of sleep over a 24-h period from the data obtained in the continuous recording of e.e.g.s from 27 to 31 days of age revealed an ultradian rhythm with a periodicity of approximately 3 0 h.6. These findings indicate that the rat GH secretary rhythm with a 3-0-h periodicity develops by 30 days of age in both sexes, relating to the 3-0-h-period ultradian rhythm of the sleep-wakefulness cycle entrained by the light cycle.

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Dynamic Studies of Growth Hormone and Prolactin Secretion in the Female Rat

Cited by 152 publications

References 6 publications

Identification of salsolinol in the mediobasal hypothalamus of lactating ewes and its relation to suckling-induced prolactin and GH release

Identification of salsolinol in the mediobasal hypothalamus of lactating ewes and its relation to suckling-induced prolactin and GH release

Levels of human and rat hypothalamic growth hormone-releasing factor as determined by specific radioimmunoassay systems.

Relationship between the three‐hour‐period sleep‐wakefulness cycle and growth hormone secretion in the immature rat.

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