Ulrich Kertscher

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There are two types of superactive agonists of gonadotropin-releasing hormone (GnRHa-I: (D-amino acid)6-GnRH and GnRHa-II: (D-amino acid)6-(desGly)10-GnRH- ethylamide) the high hormonal activity of which is understood to be due to their higher receptor affinity and their higher proteolytic stability as compared with the native GnRH sequence. Using the(More)
The pathways of in vitro degradation of the gonadotropin-releasing hormone (GnRH) analog buserelin [pGlu-His-Trp-Ser-Tyr-D-Ser(tBu)-Leu-Arg- ProNHEt, B1-9] by the rat kidney membrane fraction was investigated using high-performance liquid chromatography for the separation of the peptide products and electrospray mass spectrometry for their identification.(More)
The short-time disposition of 3H-labeled D-Ser(TBU)6-desGly10-GnRH-ethylamide ([3H]buserelin) was studied in rats after bolus intravenous and subcutaneous injections and killing the rats after 1 and 3 hr, respectively. When estimated as the percentage of the injected dose, 3H-activity within the whole blood rapidly declined from 25.5% at 2 min to 4.7% at 60(More)
The disposition of the gonadotropin-releasing hormone (GnRH) agonist buserelin was studied in male rats under conditions of long-term administration. Rats were continuously infused with about 30 pmole [3H]-buserelin/24 h subcutaneously by osmotic minipumps for 4–7 days. After killing the rats, the3H-activity of the tissues was measured and was found to be(More)
Gonadotropin-releasing hormone (GnRH) derivatives are used in cancer therapy, but relatively little is known about their metabolic fate in the organism. This paper describes the application of high-performance liquid chromatography combined with electrospray mass spectrometry to identify the degradation products resulting from the incubation of two GnRH(More)
The instability of the undecapeptide substance P (SP), a neuropeptide implicated in several physiological processes, was occasionally observed when the peptide was stored in the solid state or in solution. The aim of the present study was to identify the decomposition products of SP stored as lyophilized peptide or in aqueous neutral solution. The main(More)
The corticotropin-releasing factor (CRF; 41 amino acid residues) is a major regulatory peptide in the response to stress and is distributed over many regions of the brain. We have studied the enzymatic degradation of CRF and related peptides by the CRF-degrading enzyme(s) of the rat brain (CRF-DA) by liquid-chromatographic-mass spectrometric technique and(More)
We describe new and effective techniques for extracting proopiomelanocortin (POMC)-derived peptides from mammaliar skin. Using this methodology (hot-acid extraction) and two independent HPLC-controlled RIA systems, we identify beta-endorphin peptide in mammalian skin and demonstrate significant hair cycle-dependent fluctuations in both the skin(More)
An on-line HPLC-mass spectrometric procedure with an electrospray atmospheric pressure ionization (ESI-API) ion source was developed to identify the enzymatic degradation products (peptides) generated by incubation of human beta-endorphin (h beta E) with cultured aortic endothelial cells. The samples from the complex incubation mixture were prepurified and(More)
The pattern of bradykinin (BK; Arg1-Pro2-Pro3-Gly4-Phe5-Ser6-Pro7-Phe8-Arg9)-inact iva ting peptidases in semen of boar and ram was investigated. The degradation of BK in semen was completely abolished by the metalloprotease inhibitors EDTA and o-phenanthroline. Inhibitors of angiotensin-converting enzyme (ACE; EC 3.4.15.1) and phosphoramidon, an inhibitor(More)