TRH degradation rates vary widely between different animal species

Brewster, David; Waltham, K.

doi:10.1016/0006-2952(81)90134-9

Cited by 23 publications

(3 citation statements)

References 16 publications

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“…Since TRH metabolites cross-react in the TRH RIA by less than 1%, these findings con¬ firm previous work (Brewster & Waltham 1981) showing that TRH is stable in dog serum. Fig.…”

Section: Measurement Of Trh Ir In Plasma and Prostaticfluidsupporting

confidence: 88%

TRH pharmacokinetics and nerve stimulation evoked prostatic fluid secretion during TRH infusion in the dog

Liberman

Nogimori²,

Wu³

et al. 1989

Acta Endocrinologica

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The pharmacokinetics of TRH have been determined in man and the rat as well as other species whose serum contains TRH degrading enzymes, TRH pharmacokinetics have not been determined in the dog. This species is unusual in that its serum contains little or no TRH degrading activity. TRH pharmacokinetics were determined from measurements of plasma TRH concentrations during and following a 1-h infusion of TRH, 20 \g=m\g \m=.\ kg\ m=-\ 1 \m=.\ mi n\ m=-\ 1, into dogs bearing prostatic urethral cannula. During TRH administration prostatic fluid secretion was evoked by hypogastric nerve stimulation and the content of TRH immunoreactive material in prostatic fluid was determined. Prostatic fluid was also collected after hypogastric nerve stimulation in dogs that did not receive TRH infusion. The TRH plasma profile in TRH-infused dogs exhibited two-compartment characteristics with an initial half-time of 10.4 \ m=+-\5.4 (mean \ m=+-\ sd) min, a terminal half-time of 69.4 \ m=+-\ 24 min, and a metabolic clearance rate of 7.64 \ m=+-\ 4.48 ml\ m=. \ m i n \ m = -\ 1 \ m=. \ k g \ m = -\ 1 . These findings suggest that the half-time of TRH is longer, and its metabolic clearance rate is less, in the dog than in humans or rats. TRH administration was not associated with altered nerve induced prostatic fluid secretion. Prostatic fluid samples contained TRH immunoreactive material regardless of whether they were collected after epithelial cell stimulation with pilocarpine, or after hypogastric nerve stimulation. In contrast to previous results with vasoactive intestinal peptide, TRH does not acutely alter prostatic fluid secretion. As has been reported for prostatic tissue extracts, immunoreactive material is present in prostatic fluid and appears to arise from epithelial cells.

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“…Since TRH metabolites cross-react in the TRH RIA by less than 1%, these findings con¬ firm previous work (Brewster & Waltham 1981) showing that TRH is stable in dog serum. Fig.…”

Section: Measurement Of Trh Ir In Plasma and Prostaticfluidsupporting

confidence: 88%

TRH pharmacokinetics and nerve stimulation evoked prostatic fluid secretion during TRH infusion in the dog

Liberman

Nogimori²,

Wu³

et al. 1989

Acta Endocrinologica

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“…One stimulus for carrying out the present investigations was a recent report that beagle plasma, liver and gut are essentially free of TRH-degrading activity in vitro at 37°C (Brewster & Waltham, 1981). The absence of TRH-degrading activity in dog liver was not confirmed in the present studies, as shown in Table 1.…”

Section: Discussioncontrasting

confidence: 60%

“…1980). This species is unusual because it lacks seminal vesicles (Miller, 1971) and has been reported to lack TRH-degrading enzyme activity in plasma, liver and gut (Brewster & Waltham, 1981).…”

mentioning

confidence: 97%

Thyrotrophin releasing hormone and related peptides in canine tissues

Pekary¹,

Richkind²,

Hershman³

1983

Journal of Endocrinology

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Thyrotrophin releasing hormone (TRH)-immunoreactive peptides have been quantified in canine serum, hypothalamus, liver, pancreas, adrenal, thyroid, prostate, testis, epididymis and semen by TRH radioimmunoassay, SP-Sephadex C-25 cation exchange chromatography, Sephadex G-10 exclusion chromatography and high pressure liquid chromatography. The total concentration of TRH and TRH-like peptides was highest in the hypothalamus, followed by liver, adrenal, pancreas, thyroid, prostate, epididymis, testis and serum. All of the TRH immunoreactivity (TRH-IR) within extracts of the hypothalamus was due to TRH. On the other hand, nearly all of the TRH-IR of extracts of liver, thyroid, prostate, epididymis, testis and semen was due to TRH-homologous peptides. Adrenal and pancreatic extracts contained a greater proportion of TRH in relation to the TRH-homologous peptides. Extracts of dog serum and semen were found to contain a TRH-binding substance which reduced the retention of added TRH by cation exchangers. The half-time of disappearance (t1/2) of synthetic TRH incubated at 23 degrees C in 10% (w/v) homogenates in 0.15 M-NaCl-0.05 M-phosphate buffer, pH 7.5, ranged from 22 +/- 10 (S.D.) min for liver to 120 +/- 58 min for thyroid. The short t1/2 for TRH added to dog liver homogenates contrasted with a previous report that dog liver is essentially free of TRH-degrading activity.

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