Cardiovascular characterization of the novel organic mononitrate NDIBP in rats.

Organic nitrates are widely used to restore endogenous nitric oxide (NO) levels reduced by endothelial nitric oxide synthase dysfunction. However, these drugs are associated with undesirable side effects, including tolerance. This study aims to investigate the cardiovascular effects of the new organic nitrate 1,3-diisobutoxypropan-2-yl nitrate (NDIBP). Specifically, we assessed its effects on blood pressure, vascular reactivity, acute toxicity, and the ability to induce tolerance. In vitro and ex vivo techniques showed that NDIBP released NO both in a cell-free system and in isolated mesenteric arteries preparations through a process catalyzed by xanthine oxidoreductase. NDIBP also evoked endothelium-independent vasorelaxation, which was significantly attenuated by 2-phenyl-4,4,5,5,-tetramethylimidazoline-1-oxyl 3-oxide (PTIO, 300 µM), a nitric oxide scavenger; 1-H-[1,2,4] oxadiazolo-[4,3-a]quinoxalin-1-one (ODQ, 10 µM), a soluble guanylyl cyclase inhibitor; tetraethylammonium (TEA, 3 mM), a potassium channel blocker; febuxostat (500 nM), a xanthine oxidase inhibitor; and proadifen (10 µM), an inhibitor of cytochrome P450 enzyme. Furthermore, this organic nitrate did not induce tolerance in isolated vessels and presented low toxicity following acute oral administration. In vivo changes on cardiovascular parameters were assessed using normotensive and renovascular hypertensive rats. NDIBP evoked a reduction of blood pressure that was significantly higher in hypertensive animals. Our results suggest that NDIBP acts as a NO donor, inducing blood pressure reduction without having the undesirable effects of tolerance. Those effects seem to be mediated by activation of NO-sGC-cGMP pathway and positive modulation of K+ channels in vascular smooth muscle.

Characterization of functional activity of ABCB1 and ABCC1 proteins in eggs and embryonic cells of the sea urchin Echinometra lucunter.

ABC transporter (ATP-binding-cassette transporter) proteins have been strongly associated with the phenomenon of multidrug resistance in cancer cells. Furthermore, their physiological expression has been studied in many organisms, including bacteria, fungi, plants and vertebrate or invertebrate animals. Their widespread expression through the evolution demonstrates their relevance to the survival of living things. In the present study, we characterized the functional activity of ABCB1 and ABCC1 proteins in gametes and embryonic cells of the sea urchin Echinometra lucunter. The ABC transporter proteins' functional activity was up-regulated post-fertilization. Eggs and spermatozoa of E. lucunter accumulated more C-AM (calcein acetoxymethyl ester), a fluorescent substrate of ABCB1 and ABCC1 proteins, than embryonic cells. Verapamil, reversin 205 and indomethacin were able to increase C-AM influx in eggs and embryos. However, verapamil and reversin 205 were more efficient than indomethacin, suggesting a predominance of ABCB1 protein over ABCC1 protein activity. Multidrug resistance modulating agents, at the concentration range that inhibited ABC transporter proteins, did not block the embryonic development until blastula stage. However, inhibition of ABCB1-mediated efflux by reversin 205 circumvented resistance of embryos to the antimitotic vinca alkaloid vinblastine. Embryonic development was more efficiently blocked when colchicine was previously added to eggs than to embryos 5 min after fertilization. This set of results suggests that these proteins act as a fundamental biochemical barrier conferring a protective physiological role against toxic xenobiotics in E. lucunter embryos.