Structure-activity analysis of C-terminal endothelin analogues

Development of agonists of endothelin-1 exhibiting selectivity towards ETA receptors

(1) Endothelin-1 (ET-1) is a bicyclic 21-amino-acid peptide causing a potent and sustained vasoconstriction, mainly through the ET(A) receptor subtype. So far, no selective ET(A) agonists are described in the literature. (2) A series of truncated and chemically modified ET-1 analogues were obtained through solid-phase peptide synthesis and their biological activity was assessed on rat thoracic aorta rings (ET(A) receptors) and guinea-pig lung parenchyma strips (ET(B) receptors). (3) Structure-activity studies led to the identification of ET-1 fragments exhibiting an ET(A) selective agonistic activity. (4) In particular, [D-Lys(9)]cyclo(11-15) ET-1(9-21) was the most potent peptide. It appeared as a full agonist of ET(A) receptors, being under two orders of magnitude less potent than ET-1 (EC(50): 2.3 x 10(-7) vs 6.8 x 10(-9) M). Interestingly, even a linear formylated analogue, [Ala(11,15), Trp(For)(21)]ET-1(9-21), showed a selective ET(A) activity (EC(50): 3.0 x 10(-6) M). None of the numerous analogues of the series exhibited substantial effects in the guinea-pig lung parenchyma bioassay. (5) Thus, this study describes the first compounds showing a significant bioactivity in an ET(A) pharmacological preparation while being inactive in an ET(B) paradigm. They show that the ET-1 pharmacophores, responsible for the ET(A)-mediated actions, are located within the 9-21 segment of the molecule. Moreover, the bicyclic structure of ET-1 does not appear as essential for the ET(A)-related vasoconstriction. Results also suggest that the positive charge of the Lys(9) side chain participates in an intramolecular ionic bond with the carboxylate function of Asp(18).

An automated high-performance liquid chromatography fluorescence method for the analyses of endothelins in plasma samples

A high-performance liquid chromatographic method with fluorescence detection was developed to simultaneously analyze endothelins, a class of vasoactive peptides, in plasma samples. Sample preparation for HPLC analysis was carried out by initial stabilization of blood and plasma samples against transformation of big endothelins to mature endothelins and breakdown of mature endothelins by serine proteases, as well as oxidative modifications of endothelins. Deproteinization of plasma samples was achieved with acidified acetone, and the samples were further purified on molecular weight cutoff filters. Endothelins were separated on a reversed phase LC-318 column by gradient elution using a mobile phase containing acetonitrile and water (0.1% trifluoroacetic acid) and were analyzed by fluorescence detection (lambda(Ex), 280 nm; lambda(Em), 340). Limit of detection values were in the range of 0.2-0.5 pmol. Linear (R(2), 0.99) calibration curves were established for analyte amounts in the range of 1 to 100 pmols. Recoveries of endothelins from spiked plasma samples analyzed ranged from 60-95%. Under optimized conditions the HPLC-fluorescence method was determined to be sensitive and specific for the analysis of big endothelin-1, endothelin-1, endothelin-2, and endothelin-3 in plasma. Simultaneous measurement of these endothelins by the HPLC method should permit a better understanding of their specific roles and relationships under various pathological conditions.

Survey of the 1998 optical biosensor literature

The utilization of optical biosensors to study molecular interactions continues to expand. In 1998, 384 articles relating to the use of commercial biosensors were published in 130 different journals. While significant strides in new applications and methodology were made, a majority of the biosensor literature is of rather poor quality. Basic information about experimental conditions is often not presented and many publications fail to display the experimental data, bringing into question the credibility of the results. This review provides suggestions on how to collect, analyze and report biosensor data.