Modifications induced by plasma of gestational hypertensive women on the Na+/K+-ATPase obtained from human placenta.
In order to investigate the molecular mechanisms of the inhibition of Na+/K+-ATPase in Gestational Hypertension (GH), we incubated Na+/K+-ATPase purified from human placenta of 6 healthy normotensive women with plasma from 6 GH women and 6 healthy controls. We determined the enzyme activity by the method of Esman, and the anthroyl-ouabain-binding capacity, dissociation constant (Kd) and average lifetime values (tau) by the static and dynamic fluorescence of anthroyl-ouabain. The lipid annulus of the enzyme was studied by static and dynamic fluorescence of 1-(4-trimethylaminophenyl)-6-phenyl-1,3,5- hexatriene (TMA-DPH). The addition of total and protein-free GH plasma to normal Na+/K+-ATPase significantly inhibited the enzymatic activity even at the lowest concentration studied (1:100), as well as the ouabain-binding capacity, Kd and tau. GH plasma significantly decreased the fluorescence polarization and lifetime values of TMA-DPH. These observations indicate that the inhibition caused by GH plasma on Na+/K+-ATPase might be due to a reduction of the number of active molecules or a modification of the ouabain-binding site suggesting the existence of digitalis-like factor. A link between the modification of the lipid moiety of the enzyme and the Na+/K+-ATPase inhibition might be hypothesized.
Cester
N
N
Institutes of Obstetrics and Gynecology, University of Ancona, Italy.
Rabini
R A
RA
Tranquilli
A L
AL
Lucarelli
G
G
Salvolini
E
E
Staffolani
R
R
Amler
E
E
Zolese
G
G
Mazzanti
L
L
D000328:Adult; D001798:Blood Proteins; D004791:Enzyme Inhibitors / Q000097:blood*; D005260:Female; D006801:Humans; D006973:Hypertension / Q000097:blood*; D007700:Kinetics; D010042:Ouabain / Q000378:metabolism; D010920:Placenta / Q000201:enzymology*; D011247:Pregnancy / Q000097:blood*; D011249:Pregnancy Complications, Cardiovascular / Q000097:blood*; D012016:Reference Values; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000378:metabolism*; D013050:Spectrometry, Fluorescence
D001798:Blood Proteins; D004791:Enzyme Inhibitors; D010042:Ouabain; D000254:Sodium-Potassium-Exchanging ATPase