No abstract

A high-throughput screening (HTS) assay was developed for the Na(+),K(+)-ATPase channel in order to study rubidium uptake as a measure of the functional activity and modulation of this exchanger. The assay uses elemental rubidium as a tracer for K(+) ions. Three cell lines were used to study the exchanger, and the assay was performed in a 96-well microtiter plate format. Rb(+) uptake was carried by the CHO-K1 cells at 37 degrees C; the maximum ion influx was at 80 min of incubation of the cell line in the medium containing 5.4 mM RbCl. The cells were incubated in Rb(+) uptake buffer (5.4 mM) and with the pump blocker ouabain for 1, 2, and 3 h, respectively. A complete block of the Rb(+) uptake was observed with a 5 mM concentration of ouabain for all the three time intervals. The ouabain 50% inhibitory concentration (IC(50)) value for CHO-K1 cell line ATPase was observed to be 298 microM after 3 h of incubation. In addition, IC(50) values of 94 and 89 microM were observed at 30 min of incubation, indicating that the protocol shows reproducible results. A Z' factor higher than 0.7 was observed in the assays. These studies extend the profile of Na(+),K(+)-ATPases and demonstrate the feasibility of this HTS assay system to screen for compounds that pharmacologically modulate the function of Na(+),K(+)-ATPase.

The Kv1.3 channels expressed by human T lymphocytes are emerging as important therapeutic targets. Peptides like agitoxin and margatoxin in scorpion venom and some non-peptide small molecules are known to inhibit this channel. Since such blockers cannot be used as drugs, pharma has a need to discover effective blockers. The major limiting factor for such development has been the lack of a reliable high-throughput screening (HTS) technology. A cell-based HTS assay for this target was developed in 96-well format to facilitate screening of many candidates. The assay incorporates rubidium ion as a tracer for potassium ion, which can be analyzed by the atomic absorption spectroscopy. The assay provided a Z' factor of 0.813 with more than a 4.5-fold window of detection. The two known blockers agitoxin and margatoxin gave a 50% inhibitory concentration (IC(50)) of 1.52 and 2 nM, respectively. These values are about five- and 2.8-fold higher than their IC(50) values obtained from patch clamp. Some non-peptide compounds like tamoxifen, nifedipine, and fluoxetine also inhibited the efflux through these channels, whereas astemizole and pimozide (potent human ether-a-go-go-related gene blockers) did not block Kv1.3 activity.

A high-throughput screening (HTS) assay was developed for cotransporter, NKCC1, which is a potential target for the treatment of diverse disorders. This nonradioactive rubidium flux assay coupled with ion channel reader series provides a working screen for this target expressed in human embryonic kidney (HEK) cell line. An eightfold window of detection was achieved with the optimized assay. This new functional assay offered a robust working model for NKCC1 in determining reliable and concordant rank orders of the test compounds supporting its sensitivity and specificity. The robustness of manual assay indicated by Z' of 0.9 qualified its amenability to automation. The Z' of 0.7 was displayed by automated assay employed in high-throughput screening of compound libraries against this target. Being electrically neutral, the NKCC1 screening is difficult to achieve by both manual and automated electrophysiological techniques. These techniques, although considered gold standard, suffer from their inherent problems of being too slow to be in high-throughput format and with high running costs. In addition to being a functional assay for NKCC1, it is nontoxic as compared with thallium flux assay, which is prone to generate high number of false-positive/false-negative rates because of its innate fluorescence issues.

While meeting the pandemic demand of SARS-CoV-2 testing, clinical laboratories worldwide tend to adopt new test systems offering cost-effective and faster test outcomes. However, the reliability of SARS-CoV-2 test results has paramount importance in the management of such a health crisis. Therefore, this study sought to determine the accuracy of the test results from a novel duplex Microchip RT-PCR test system using patient saliva samples and nasal swabs stabilized in Viral Transport Medium (VTM) with reference threshold Cycle Values (Ct). The VTM used to stabilize these samples during transport was found to be inhibitory to the RT-PCR. Therefore, all the samples were subjected to spin column purification of total RNA to remove the influence of VTM. A total of 70 patient samples, including 24 positive-and 31 negative-saliva in VTM samples and 15 positive nasal swab samples, were tested. Results obtained from both the sample types were compared to their reference values and no false positive or false negatives were observed. From this data, accuracy, specificity, and sensitivity were determined to be 100% applying the corresponding formulae. The limit of detection with 95% confidence probability was determined to be 2.5 copies/µl in the original sample.