Protein phosphatase inhibitors prolong Ca(2+)-transients and divalent cation-dependent action potentials in leech Retzius cells.
Elevation of [K+]o for 30 s from 4 to 120 mM produced a fast and reversible depolarization and transient increase in [Ca2+]i in fura-2 loaded Retzius cells of the leech. The protein phosphatase inhibitor, okadaic acid, significantly slowed the return of [Ca2+]i toward baseline without affecting the amplitude of depolarization or rate of repolarization. Furthermore, okadaic acid and another phosphatase inhibitor, calyculin A, prolonged Ba(2+)-dependent action potentials. These results suggest that the kinetics of Ca2+ influx may be regulated by the activity of phosphatases PP-1 and/or PP-2A.
Department of Cell Biology and Anatomy, New York Medical College, Valhalla 10595.
A L
AL
Kleinhaus
R J
RJ
Zeman
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002413:Cations, Divalent / Q000494:pharmacology*; D004988:Ethers, Cyclic / Q000494:pharmacology; D016257:Fura-2; D017952:Ganglia, Invertebrate / Q000166:cytology / Q000502:physiology; D007865:Leeches / Q000378:metabolism*; D008387:Marine Toxins; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009412:Nerve Fibers / Q000187:drug effects*; D019319:Okadaic Acid; D010080:Oxazoles / Q000494:pharmacology; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors*; D011506:Proteins / Q000494:pharmacology*
D002413:Cations, Divalent; D004988:Ethers, Cyclic; D008387:Marine Toxins; D010080:Oxazoles; D011506:Proteins; D019319:Okadaic Acid; C059041:calyculin A; D010749:Phosphoprotein Phosphatases; D002118:Calcium; D016257:Fura-2