Document Detail

Permeability characteristics of erythrocyte membrane to okadaic acid and calyculin A.
MedLine Citation:
PMID:  8779906     Owner:  NLM     Status:  MEDLINE    
The rates of transport of the protein phosphatase inhibitors okadaic acid and calyculin A through rabbit erythrocyte membranes have been estimated by measuring protein phosphatase type 2A (PP2A) activity in lysates. High concentrations of okadaic acid (100 nM) cause rapid (t 1/2 approximately 10 min) inhibition of PP2A. However, the t 1/2 for okadaic acid influx is much longer because the concentration is much higher than the concentration inhibiting 50% of the maximal response (IC50). The estimated t 1/2 is over 1 h at 37 degrees C and over 4 h at 25 degrees C. The effect of low extracellular pH indicates that the undissociated acid is the permeant species. It takes hours to reverse the effect of okadaic acid, because the efflux must proceed through several half times before the concentration is below the IC50 for PP2A. The permeation of calyculin A in contrast to okadaic acid is too fast to measure at 25 degrees C. Our results indicate that okadaic acid entry into erythrocytes is slower than is generally believed; it is crucial to consider concentration, temperature, pH, and time of exposure to okadaic acid to interpret the effects of this agent on intact cells.
A N Namboodiripad; M L Jennings
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  The American journal of physiology     Volume:  270     ISSN:  0002-9513     ISO Abbreviation:  Am. J. Physiol.     Publication Date:  1996 Feb 
Date Detail:
Created Date:  1996-12-20     Completed Date:  1996-12-20     Revised Date:  2007-11-15    
Medline Journal Info:
Nlm Unique ID:  0370511     Medline TA:  Am J Physiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  C449-56     Citation Subset:  IM    
Department of Physiology and Biophysics, University of Texas Medical Branch, Galveston 77555-0641, USA.
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MeSH Terms
Cell Membrane Permeability
Dose-Response Relationship, Drug
Erythrocyte Membrane / metabolism*
Okadaic Acid / pharmacokinetics*
Osmolar Concentration
Oxazoles / pharmacokinetics*
Phosphoprotein Phosphatases / antagonists & inhibitors
Rabbits / blood
Time Factors
Grant Support
Reg. No./Substance:
0/Oxazoles; 101932-71-2/calyculin A; 78111-17-8/Okadaic Acid; EC Phosphatases

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