The TRH‐like peptides in rabbit testis are different from the TRH‐like peptide in the prostate

Linden, H.U.; García, Jesús del Río; Huber, Ariana; Kreil, Günther; Smyth, Derek G.

doi:10.1016/0014-5793(95)01468-3

Cited by 14 publications

(9 citation statements)

References 18 publications

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“…1,13) and cross-react, to varying extents, with antisera raised against TRH (6, 14 -16). In human prostate and seminal fluid ϽEQP-NH 2 and ϽEFP-NH 2 have been identified (17)(18)(19), whereas ϽEYP-NH 2 has been found in alfalfa (20). Another TRH-like peptide is ϽEEP-NH 2 , which has been detected in pituitary, prostate, and seminal fluid of various mammalian species (including man, rat, and rabbit) (7,8,(21)(22)(23)(24)(25).…”

mentioning

confidence: 99%

Renal Clearance of the Thyrotropin-Releasing Hormone-Like Peptide Pyroglutamyl-Glutamyl-Prolineamide in Humans

Klootwijk¹

1997

Journal of Clinical Endocrinology & Metabolism

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TRH-like peptides have been identified that differ from TRH (pGlu-His-ProNH2) in the middle amino acid. We have estimated TRH-like immunoreactivity (TRH-LI) in human serum and urine by RIA with TRH-specific antiserum 8880 or with antiserum 4319, which binds most peptides with the structure pGlu-X-ProNH2. TRH was undetectable in serum (< 25 pg/mL), but TRH-LI was detected with antiserum 4319 in serum of 27 normal subjects, 21 control patients, and 12 patients with carcinoid tumors (range 17-45, 5-79, and 18-16,600 pg/mL, respectively). Because serum was kept for at least 2 h at room temperature, which causes degradation of TRH, pGlu-Phe-ProNH2, and pGlu-Tyr-ProNH2, serum TRH-LI is not caused by these peptides. On high-performance liquid chromatography, serum TRH-LI coeluted with pGlu-Glu-ProNH2 (< EEP-NH2), a peptide produced in, among others, the prostate. Urine of normals and control patients also contained TRH-LI (range 1.14-4.97 and 0.24-5.51 ng/mL, respectively), with similar levels in males and females. TRH represented only 2% of urinary TRH-LI, and anion-exchange chromatography and high-performance liquid chromatography revealed that most TRH-LI in urine was < EEP-NH2. In patients with carcinoid tumors, increased urinary TRH-LI levels were noted (range 1.35-962.4 ng/mL). Urinary TRH-LI correlated positively with urinary creatinine, and the urinary clearance rate of TRH-LI was similar to the glomerular filtration rate. In addition, serum TRH-LI was increased in 17 hemodialysis patients (43-373 pg/mL). This suggests that serum < EEP-NH2 is cleared by glomerular filtration with little tubular resorption. The possible role of the prostate as a source of urinary TRH-LI was evaluated in 11 men with prostate cancer, showing a 25% decrease in urinary TRH-LI excretion after prostatectomy (0.19 +/- 0.02 vs. 0.15 +/- 0.01 ng/mumol creatinine, mean +/- SEM). However, TRH-LI was similar in spontaneously voided urine and in urine obtained through a nephrostomy cannula from 16 patients with unilateral urinary tract obstruction (0.15 +/- 0.01 vs. 0.14 +/- 0.01 ng/mumol creatinine). These data indicate that: 1) TRH-LI in human serum represents largely < EEP-NH2, which is cleared by renal excretion; 2) part of urinary < EEP-NH2 is derived from prostatic secretion into the blood and not directly into urine; and 3) urinary < EEP-NH2 can be used as marker for carcinoid tumors.

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confidence: 99%

Renal Clearance of the Thyrotropin-Releasing Hormone-Like Peptide Pyroglutamyl-Glutamyl-Prolineamide in Humans

Klootwijk¹

1997

Journal of Clinical Endocrinology & Metabolism

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“…An N-extended form of TRH-like peptides was observed in substantial concentration in human plasma (Ruiz-Alcaraz and del Rio-Garcia 2003) or in human semen (Khan and Smyth 1993). The analysis of rabbit prostate and testis have shown that in contrast to the prostate, testis contains high concentrations of N-extended form of pEFPam, but essentially no tripeptide (Linden et al 1996). Similar results were found in human testis and prostate (Bilek et al 1994).…”

Section: Introductionmentioning

confidence: 71%

TRH-Like Peptides

Bílek

Bičı́ková²,

Safarík³

2011

Physiol Res

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TRH-like peptides are characterized by substitution of basic amino acid histidine (related to authentic TRH) with neutral or acidic amino acid, like glutamic acid, phenylalanine, glutamine, tyrosine, leucin, valin, aspartic acid and asparagine. The presence of extrahypothalamic TRH-like peptides was reported in peripheral tissues including gastrointestinal tract, placenta, neural tissues, male reproductive system and certain endocrine tissues. Work deals with the biological function of TRH-like peptides in different parts of organisms where various mechanisms may serve for realisation of biological function of TRH-like peptides as negative feedback to the pituitary exerted by the TRH-like peptides, the role of pEEPam such as fertilization-promoting peptide, the mechanism influencing the proliferative ability of prostatic tissues, the neuroprotective and antidepressant function of TRH-like peptides in brain and the regulation of thyroid status by TRH-like peptides.

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“…Although it was initially suggested that TRH-like peptides, other than TRH, were not detectable in brain (Rondeel et al, 1995a;Rondeel et al, 1995b), it was later shown that, among other, Gln-Tyr-Pro-NH 2 , and Gln-Phe-Pro-NH 2 are present in brain (Pekary et al, 2004;Pekary et al, 2005). To our knowledge, although these peptides are likely the product of posttranslational processing of precursor peptides (Linden et al, 1996), the precursors are still unknown. However, they may act as intercellular messengers, including in the brain, since their concentrations can vary rapidly in response to some stimuli, suggesting changes in synthesis and/or release (Pekary and Sattin, 2012;Pekary et al, 2015), and there is direct evidence that a peptide similar to Gln-Phe-Pro-NH 2 can be released into hypothalamic extracellular space in vitro (Meńdez et al, 1999).…”

Section: Trhde Gene Transcripts Protein Structure Isoforms and Spementioning

confidence: 95%

The Thyrotropin-Releasing Hormone-Degrading Ectoenzyme, a Therapeutic Target?

et al. 2020

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Thyrotropin releasing hormone (TRH: Glp-His-Pro-NH 2) is a peptide mainly produced by brain neurons. In mammals, hypophysiotropic TRH neurons of the paraventricular nucleus of the hypothalamus integrate metabolic information and drive the secretion of thyrotropin from the anterior pituitary, and thus the activity of the thyroid axis. Other hypothalamic or extrahypothalamic TRH neurons have less understood functions although pharmacological studies have shown that TRH has multiple central effects, such as promoting arousal, anorexia and anxiolysis, as well as controlling gastric, cardiac and respiratory autonomic functions. Two G-protein-coupled TRH receptors (TRH-R1 and TRH-R2) transduce TRH effects in some mammals although humans lack TRH-R2. TRH effects are of short duration, in part because the peptide is hydrolyzed in blood and extracellular space by a M1 family metallopeptidase, the TRH-degrading ectoenzyme (TRH-DE), also called pyroglutamyl peptidase II. TRH-DE is enriched in various brain regions but is also expressed in peripheral tissues including the anterior pituitary and the liver, which secretes a soluble form into blood. Among the M1 metallopeptidases, TRH-DE is the only member with a very narrow specificity; its best characterized biological substrate is TRH, making it a target for the specific manipulation of TRH activity. Two other substrates of TRH-DE, Glp-Phe-Pro-NH 2 and Glp-Tyr-Pro-NH 2, are also present in many tissues. Analogs of TRH resistant to hydrolysis by TRH-DE have prolonged central efficiency. Structure-activity studies allowed the identification of residues critical for activity and specificity. Research with specific inhibitors has confirmed that TRH-DE controls TRH actions. TRH-DE expression by b2-tanycytes of the median eminence of the hypothalamus allows the control of TRH flux into the hypothalamus-pituitary portal vessels and may regulate serum thyrotropin secretion. In this review we describe the critical evidences that suggest that modification of TRH-DE activity in tanycytes, and/or in other brain regions, may generate beneficial consequences in some central and metabolic disorders and identify potential drawbacks and missing information needed to test these hypotheses.

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The TRH‐like peptides in rabbit testis are different from the TRH‐like peptide in the prostate

Cited by 14 publications

References 18 publications

Renal Clearance of the Thyrotropin-Releasing Hormone-Like Peptide Pyroglutamyl-Glutamyl-Prolineamide in Humans

Renal Clearance of the Thyrotropin-Releasing Hormone-Like Peptide Pyroglutamyl-Glutamyl-Prolineamide in Humans

TRH-Like Peptides

The Thyrotropin-Releasing Hormone-Degrading Ectoenzyme, a Therapeutic Target?

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