Differences in the degradation of hypothalamic releasing factors by rat and human serum

Benuck, M.; Marks, Neville

doi:10.1016/0024-3205(76)90263-0

Cited by 77 publications

(25 citation statements)

References 22 publications

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“…This procedure is highly recommended for the effec tive recovery of LHRH from plasma or serum and for the removal of blood proteins that are believed to interfere with the radioimmunoassay [2,24], In addition, disagreement still persists as regards the breakdown of LHRH In blood. Some workers believe LHRH is relatively stable in plasma, even at 37 °C [21], whereas others claim this decapeptide is enzymatically cleaved [4,24, 33]. Since thyrotropin-releas ing hormone (TRH) peptidase activity has been reported in the stalk plasma of the rat [23], it is possible that this plasma contains degrading enzymes for LHRH.…”

mentioning

confidence: 99%

Correlative Surges of LHRH, LH and FSH in Pituitary Stalk Plasma and Systemic Plasma of Rat during Proestrus

Ching¹

1982

Neuroendocrinology

102

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An effective recovery procedure has been utilized for determining luteinizing hormone-releasing hormone (LHRH) concentrations in rat pituitary stalk plasma. With this new recovery protocol it was revealed that stalk plasma immunoreactive LHRH concentrations increased 5-fold to 206 pg/ml during proestrus (p < 0.001) and decreased to diestrous levels during estrus. In contrast, the LHRH concentration in systemic plasma extracts remained unchanged throughout the estrous cycle and did not exceed 4 pg/ml. The stalk plasma:systemic plasma ratio increased from 12:1 at diestrus to 76:1 at proestrus; it then decreased to 22:1 at estrus (p < 0.001). Correlative luteinizing hormone (LH) and follicle-stimulating hormone (FSH) surges of statistically significant magnitudes were observed in the systemic plasma of nonanesthetized cardiac-catheterized rats during proestrus. When administered before the onset of the critical period, Althesin and other anesthetic agents suppressed but did not completely inhibit the peripheral LH surge in cardiac-catheterized rats.The FSH surge was suppressed also but to a lesser degree. These results indicate that the brain triggers the preovulatory surge of LH and FSH via massive secretion of LHRHinto the pituitary portal circulation. They also reveal that, aside from any dosage considerations, the type of anesthetic used and the time of administration in relation to the critical period, can significantly affect the magnitude of pituitary LH and FSH secretion.

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mentioning

confidence: 99%

Correlative Surges of LHRH, LH and FSH in Pituitary Stalk Plasma and Systemic Plasma of Rat during Proestrus

Ching¹

1982

Neuroendocrinology

102

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“…Degradation of hypothalamic hormones by peptidases in rat and human serum has already been reported (15) and has been postulated to cause high "blank effects" in one radioimmunoassay for somatostatin (16). Nevertheless, enzymic degradation of the tracer is probably an underestimated problem in validating a radioimmunoassay system (17).…”

Section: Discussionmentioning

confidence: 95%

Evidence for a Nonspecific Factor Interfering in the Radioimmunoassay of Somatoliberin-Like Immunoreactivity in Human Seminal Plasma

Losa¹,

Wolfram²,

Schopohl³

et al. 1988

Clinical Chemistry and Laboratory Medicine

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In the present study we investigated the nature of somatoliberin-like immunoreactivity in human seminal plasma. In unextracted seminal plasma, somatoliberin-like immuno reactivity represented 3.8 §/1 somatoliberiii, with a dilution curve that ran almost completely parallel to that of synthetic somatoliberin standard. After extraction by adsorption on hydrophobic CIS Sep-pak cartridges or immunoaffmity chromatography, no somatoliberin-like immunoreactivity in seminal plasma could be detected. After gel permeation chromatography on a Sephadex G-50 fine column, all somatoliberin-like immunoreactivity of unextracted seminal plasma was recovered at the void volume of the column. When equal volumes of unextracted seminal plasma and radioiodinated somatoliberin were coincubated for two days at 4 °C, gel chromatography revealed the disappearance of the normal [ J?5 I]somatoliberin peak, replaced by a new peak eluting shortly after the total volume of the column. When unextracted seminal plasma was heated at 90 °C for 10 min or submitted to ultrafiltration, the interfering factor was no longer detectable. Our data show that enzymic degradation of radioiodinated somatoliberin led to misleadingly high concentrations of somatoliberin-like immunoreactivity in seminal plasma. These phenomena should therefore be considered when performing radioimmunoassays of short chain peptides in biological fluids.

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“…Elongation of the side chain (pGln(Gly)2D-Trp8-somatostatin) resulted in a compound with greater potency than cyclic-somatostatin. The greater activity might in part be due to the D-Trp8 substitution and/or in part due to a greater biological half-life, a result of elongation 11 M. P. BROWN AND OTHERS of the side chain, although the N-terminal of somatostatin is not reported as being an important site of degradation (Benuck & Marks, 1976).…”

Section: Discussionmentioning

confidence: 99%

Structure‐activity relationships of eighteen somatostatin analogues on gastric secretion.

Brown¹,

Coy²,

Gómez-Pan³

et al. 1978

The Journal of Physiology

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SUMMARY1. The effect of somatostatin and eighteen somatostatin analogues on pentagastrin-stimulated gastric acid and pepsin secretion was investigated in the conscious vagotomized cat prepared with chronic gastric fistulae. The majority of the analogues are peptides where D-amino acids are incorporated into the molecule instead of the natural L-isomers.2. The ID50 for cyclic-somatostatin inhibition of near-maximal gastric acid secretion stimulated by pentagastrin 8 jug kg-1 hr-1 was found to be 1-29 + 0-13 n-mole kg-1 hr-1. Pentagastrin-stimulated pepsin secretion had a lower threshold to somatostatin inhibition than did acid secretion.3. D-Phe6, D-Phe7, D-Thr10, D-Thr12 and D-Phe6-D-Trp5 analogues all show low biological activity against the secretion of gastric acid and pepsin, growth hormone, insulin and glucagon. None of these analogues are antagonists of the cyclic-somatostatin inhibition of gastric secretion, suggesting that they have low affinity for this somatostatin receptor.4. The analogues under investigation show parallel changes in activity against gastric and growth hormone secretion, suggesting a similarity between the gastric and growth hormone receptors for somatostatin.5. D-Cys14 analogues are equipotent with or have a greater potency than cyclicsomatostatin in inhibiting the secretion of gastric acid, growth hormone and glucagon but show low insulin inhibiting activity.

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Differences in the degradation of hypothalamic releasing factors by rat and human serum

Cited by 77 publications

References 22 publications

Correlative Surges of LHRH, LH and FSH in Pituitary Stalk Plasma and Systemic Plasma of Rat during Proestrus

Correlative Surges of LHRH, LH and FSH in Pituitary Stalk Plasma and Systemic Plasma of Rat during Proestrus

Evidence for a Nonspecific Factor Interfering in the Radioimmunoassay of Somatoliberin-Like Immunoreactivity in Human Seminal Plasma

Structure‐activity relationships of eighteen somatostatin analogues on gastric secretion.

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