Mutational Analysis of the Analgesic Peptide DrTx(1-42) Revealing a Functional Role of the Amino-Terminal Turn

Background: DrTx(1-42) (a carboxyl-terminally truncated version of drosotoxin) is a potent and selective blocker of tetrodotoxin-resistant (TTX-R) Na + channels in rat dorsal root ganglion neurons with analgesic activity. This purpose is to identify key amino acids which are responsible for both blocking and analgesic effects of DrTx(1-42). Methods: On the basis of previous study, we designed five mutants of DrTx(1-42) (delN, D8A, D8K, G9A, and G9R) in the amino-terminal turn (N-turn) region, a proposed functional region located in the amino-terminus of the molecule. All these mutants were expressed in E.coli and purified by RP-HPLC. Electrophysiological properties of these analogues were examined by whole-cell patch-clamp recordings and their antinociceptive effects were investigated by the formalin test and acetic acid induced writhing test. Results: All the mutants except for G9A possess a similar secondary structure to that of DrTx(1-42), as identified by circular dichroism analysis. Three mutants (delN, D8A and G9A) were found almost inactive to TTX-R Na + channels, whereas D8K retains similar activity and G9R showed decreased potency when compared with the wild-type molecule. Consistent with the electrophysiological observations, D8K and G9R exhibited antinociceptive effects in the second phase (inflammatory pain) of the formalin test and the acetic acid induced writhing test, while delN, D8A and G9A lack such effects. Conclusions: Our results show that the N-turn is closely related to function of DrTx(1-42). The mutant (D8A) as a contro

Changes In Sperm Parameters Following Administration Of Theophylline, A Competitive Antagonist Of Adenosine In Rats Exposed To Bleomycin, A Chemotherapeutic Agent

The aim of the present study is to determine the effects of theophylline (THP), a methylxanthine derivative, on the sperm parameters of rats exposed to bleomycin (BLM) as a chemotherapeutic agent. The study was performed on 32 male rats. The rats in Group 1 were administered only with sterile saline intratracheally. The rats in Group 2 were administered a single dose of 7.5 mg/kg of BLM intratracheally. The rats in Group 3 received a single dose of 7.5 mg/kg of BLM intratracheally. In addition, THP was administered to rats in Group 3 intraperitoneally at a dose of 75 mg/kg/ day for 14 days. The rats in group 4 were administered an intraperitoneal injection of THP at a dose of 75 mg/kg/day for 14 days. Motility, sperm density, abnormal sperm and dead sperm rates were examined. Significant deteriorations were observed in sperm parameters of rats that were administered BLM. In sperm parameters of rats that were administered THP, it was determined that it only increased motility, but did not significantly change sperm density, abnormal sperm and dead sperm count. In this study, THP only increased motility. There was no positive effect on sperm parameters except motility. © 2019 Ataturk Universitesi. All rights reserved.Scopu