Abstract
Studies on the action of ouabain and digitoxin on contractile function of rabbit myometrium showed that both the glycosides (5 x 10-7 M) potentiated acetylcholine-induced contractions within 10 minutes and this action disappeared on washing with drug-free normal Krebs-Ringer solution within 10 minutes. The binding of 3H-ouabain (5 x 10-7 M) to plasma membrane fraction, however, did not wash off completely in 10 minutes (only 23% of total ouabain bound was released) and also this binding was not decreased by 23 mM K+ in 10 minutes, though K+-free Krebs-Ringer solution increased the binding in 10 minutes. Thus, the contractile effect of ouabain occurring after 10 minutes in normal Krebs-Ringer solution may not be related to the binding of these drugs to Na+-K+-adenosine triphosphatase (ATPase). Studies on the effect of ouabain and digitoxin on ion recovery of Na+-rich tissues showed that 5 x 10-7 M ouabain or digitoxin did not inhibit ion recovery in 10 minutes. Even 10-5 M ouabain or digitoxin did not inhibit ion recovery in 10 minutes. On 30 minutes exposure, all the concentrations inhibited ion recovery (30% with 5 x 10-7 or 10-6 M and 50% with 10-5 M compared to controls). These results suggest that inhibition of Na+-K+-ATPase is not the mechanism of potentiation of contractile effect as these two effects could be dissociated.
Footnotes
- Received February 5, 1973.
- Accepted November 15, 1973.
- © 1974 by The Williams & Wilkins Co.
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