Regulation of the Na,K-ATPase activity of Madin-Darby canine kidney cells in defined medium by prostaglandin E1 and 8-bromocyclic AMP.
The role of PGE1 in regulating the activity of the Na+, K(+)-ATPase in Madin Darby Canine Kidney (MDCK) cells has been examined. PGE1 increased the initial rate of ouabain-sensitive Rb+ uptake by MDCK cells, a process that continued to occur over a 5-day period. The increase in the initial rate of ouabain-sensitive Rb+ uptake in MDCK cells treated with PGE1 could be explained by a 1.6-fold increase in the Vmax for ouabain-sensitive Rb+ uptake. The increase in the Vmax for ouabain-sensitive Rb+ uptake observed in MDCK cells under these conditions can be explained either by an increase in the number of active Na+ pumps, or by an increase in the efficiency of the Na+ pumps. Consistent with the former possibility is the observed increase in the number of ouabain binding sites, as well as the increase in Na+, K(+)-ATPase activity in cell lysates obtained from MDCK monolayers treated with PGE1. The involvement of cyclic AMP in mediating these effects of PGE1 on the Na+, K(+)-ATPase in MDCK cells is supported by: (1) the observation of similar effects in 8-bromocyclic AMP treated MDCK monolayers, and (2) a dramatic reduction of the stimulatory effects of PGE1 and 8-bromocyclic AMP on the Vmax for ouabain-sensitive Rb+ uptake, and on the number of ouabain binding sites in dibutyryl cyclic AMP resistant clone 3 (DBr3) (which is defective in cyclic AMP dependent protein kinase activity). PGE1 independent MDCK monolayers exhibit both an increase in the Vmax for ouabain-sensitive Rb+ uptake and an increase in the number of ouabain binding sites in response to 8-bromocyclic AMP. Apparently, the cyclic AMP phosphodiesterase defect in these PGE1 independent cells did not cause cellular cyclic AMP levels to be elevated to a sufficient extent to maximally increase the Na+, K(+)-ATPase activity in these variant cells.
Taub
M L
ML
Biochemistry Department, State University of New York, Buffalo 14214.
Wang
Y
Y
Yang
I S
IS
Fiorella
P
P
Lee
S M
SM
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology*; D000527:Alprostadil / Q000494:pharmacology*; D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D002460:Cell Line; D003470:Culture Media; D004285:Dogs; D004351:Drug Resistance; D014644:Genetic Variation; D007425:Intracellular Membranes / Q000378:metabolism; D007477:Ions; D007668:Kidney / Q000166:cytology / Q000201:enzymology* / Q000378:metabolism; D010042:Ouabain / Q000378:metabolism; D012016:Reference Values; D012413:Rubidium / Q000493:pharmacokinetics; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
D003470:Culture Media; D007477:Ions; D015124:8-Bromo Cyclic Adenosine Monophosphate; D010042:Ouabain; D003994:Bucladesine; D000254:Sodium-Potassium-Exchanging ATPase; D000527:Alprostadil; D012413:Rubidium