Injection Of Bumetanide Research Articles

Functional Significance of the Excitatory Effects of GABA in the Suprachiasmatic Nucleus

Over 90% of neurons within the suprachiasmatic nucleus (SCN) express γ-aminobutyric acid (GABA). Although GABA is primarily an inhibitory neurotransmitter, in vitro studies suggest that the activation of GABAA receptors (GABAAR) elicits excitation in the adult SCN. The ratio of excitatory to inhibitory responses to GABA depends on the balance of chloride influx by Na+-K+-Cl- cotransporter 1 (NKCC1) and chloride efflux by K+-Cl- cotransporters (KCCs). Excitatory responses to GABA can be blocked by inhibition of the inward chloride cotransporter, NKCC1, with the loop diuretic bumetanide. Here we investigated the role of NKCC1 activity in phase shifting the circadian pacemaker in response to photic and nonphotic signals in male Syrian hamsters housed in constant darkness. In the early subjective night (CT 13.5), injection of bumetanide into the SCN reduced light-induced phase delays. However, during the late subjective night (CT 19), bumetanide administration did not alter light-induced phase advances. Injection of bumetanide during the subjective day (CT 6) did not alter the phase of free-running circadian rhythms but attenuated phase advances induced by injection of the GABAAR agonist muscimol into the SCN. These data support the hypothesis that the excitatory effects of endogenously released GABA contribute to the ability of light to induce phase delays, thereby contributing to the most important function of the circadian system, its entrainment with the day-night cycle. Further, the finding that bumetanide inhibits the phase-advancing effects of muscimol during the subjective day supports the hypothesis that the excitatory responses to GABA also contribute to the ability of nonphotic stimuli to phase shift the circadian pacemaker.

The effect of bumetanide on photodynamic therapy‐induced peri‐tumor edema of C6 glioma xenografts

The aim of this study was to investigate the effect of bumetanide on peri-tumor edema caused by photodynamic therapy (PDT) of intraparenchymal C6 glioma xenografts. Seven days after inoculation with C6 cells, rats with MRI-confirmed glioma received hematoporphyrin monomethyl ether (HMME)-mediated PDT, injection of bumetanide or a combination of the two treatments. After treatment, tumor volume, tumor weight, brain water content, microvessel density, expression of NKCC-1, Zonula occludens-1 (ZO-1), and animal survival time were examined. In the PDT group, tumor growth was significantly inhibited and survival prolonged. Bumetanide enhanced the efficacy of PDT and reduced PDT-induced peri-tumor edema in the combined PDT + bumetanide treatment group where NKCC-1 expression in response to PDT was significantly suppressed. ZO-1 expression was significantly suppressed in the PDT-only group. This suppression was not observed in the combined PDT + bumetanide treatment group. PDT, in combination with bumetanide was seen to significantly inhibit the growth of C6 glioma, relieve peri-tumor edema caused by PDT alone and prolong survival. These results suggest that PDT, in combination with bumetanide, may be a useful and promising strategy in the treatment of human glioma.

Sensitive isotope dilution liquid chromatography/tandem mass spectrometry method for quantitative analysis of bumetanide in serum and brain tissue

We have developed and validated a simple and sensitive stable isotope dilution liquid chromatography/tandem mass spectrometric (LC–MS/MS) method for the quantification of bumetanide in human serum. Samples were prepared with a simple acetonitrile based protein precipitation. The supernatant was then analyzed directly using LC–MS/MS. Chromatographic separation was achieved on a C18 reversed phase column using a methanol and water gradient. The detection was performed in selected reaction monitoring (SRM) mode via a positive electrospray ionization (ESI) interface. The method had a lower limit of quantification (LLOQ) of 1 ng/mL, linearity up to 1250 ng/mL, intra- and inter-day precision less than 10%, and accuracy within ±10%. This method was also demonstrated to be suitable for the analysis of bumetanide in rat serum and brain tissue. Bumetanide concentrations in rat serum and brain were determined for samples collected at several intervals following intraperitoneal (i.p.) injection of bumetanide, and were used to calculate bumetanide permeability through the blood–brain barrier.