In vitro selection for different mutational patterns in the HIV-1 reverse transcriptase using high and low selective pressure of the nonnucleoside reverse transcriptase inhibitor HBY 097 |
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Authors: | JP Kleim I Winkler M R?sner R Kirsch H Rübsamen-Waigmann A Paessens G Riess |
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Affiliation: | Department of Pharmacology and Clinical Pharmacology, St. George's Hospital Medical School, Cranmer Terrace, London SW17 0RE, UK. |
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Abstract: | Measurement of Na-Ca exchange activity was used to examine subsarcolemmal sodium levels ([Na+]s) in single, voltage-clamped guinea-pig cardiac myocytes while Na-K pump activity was modulated pharmacologically. Changes in Nas were evaluated from phase-plane analysis of the changes in intracellular calcium, measured using the fluorescent indicators Fura-red and Fluo-3. Activation of beta-adrenoceptors with 1 microM isoprenaline resulted in activation of the cAMP-dependent chloride current, but had no effect on the calcium transient mediated via the Na-Ca exchanger, regardless of whether the Na-K pump was active or inhibited (with strophanthidin). The ability of Na-Ca exchange activity to report [Na+]s was demonstrated by the effect of changing the extracellular rubidium concentration from 1 to 5.4 mM to modulate Na-K pump activity. We suggest that beta-adrenergic stimulation does not directly affect either the Na-K pump or the Na-Ca exchanger and that the Na-Ca exchanger can be used as a sensitive indicator of changes in [Na+]s and Na-K pump activity. |
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