Can maximum ouabain-sensitive 86Rb+ uptake rate be obtained by increasing Na+ influx?
Increasing stimulation frequency and monensin were utilized in attempts to enhance Na+ influx and thereby elicit the maximum rate of ouabain-sensitive 86Rb+ uptake in rat atrial muscle. Increasing stimulation frequency between 0 and 9 Hz enhanced the rate of ouabain-sensitive 86Rb+ uptake, whereas the uptake rate appeared to decrease at higher frequencies. Monensin (1.0-5.0 microM) increased the rate of uptake in atrial preparations stimulated at 6 Hz. A higher concentration of monensin produced a significant decline in uptake rate. The maximum rate of ouabain-sensitive 86Rb+ uptake produced by monensin in preparations stimulated at 6 Hz was not significantly different from the maximum elicited by stimulation frequency alone. The results suggest that either method of increasing Na+ influx may be used to maximize the rate of ouabain-sensitive 86Rb+ uptake and thereby estimate the Na+ pump capacity of rat atrial muscle; however, it is possible that the inhibitory actions which were apparent at very high levels of monensin and stimulation frequency may mask the true maximum value.
D000818:Animals; D004558:Electric Stimulation; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects*; D007700:Kinetics; D008297:Male; D008985:Monensin / Q000494:pharmacology; D009200:Myocardial Contraction / Q000187:drug effects; D009206:Myocardium / Q000378:metabolism; D010042:Ouabain / Q000494:pharmacology*; D011868:Radioisotopes; D051381:Rats; D012413:Rubidium / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism* / Q000502:physiology
D007473:Ion Channels; D011868:Radioisotopes; D010042:Ouabain; D008985:Monensin; D012964:Sodium; D012413:Rubidium