Human hypertensive placenta contains an increased amount of Na,K-ATPase with higher affinity for cardiac glycosides.
Placentas of women suffering from pregnancy-induced hypertension (PIH) were found to contain a greater amount of Na,K-ATPase molecules, estimated from anthroyl ouabain binding, than normotensive individuals. Both the microsomal fraction of placental cells and purified Na,K-ATPase showed an increased affinity for the specific inhibitor ouabain which, in the case of the microsomes, bound with a dissociation constant of 0.9 nM as compared with 3.4 nM in the controls. Likewise, the dissociation constant of the ouabain complex with purified Na,K-ATPase was about 3.5 times lower in the hypertensive patients. The differences are apparently caused by a different microenvironment of the ouabain-binding site, as reflected in the quantum yield of bound anthroyl ouabain. If an endogenous digitalis-like factor is present in the body fluids to regulate Na,K-ATPase activity, the present results render its role quite plausible.
Amler
E
E
Institute of Physiology, CzAcadSci, Prague, Czech Republic.
Cester
N
N
Salvolini
E
E
Staffolani
R
R
Burkhard
M
M
Mazzanti
L
L
Kotyk
A
A
Romanini
C
C
D000328:Adult; D002301:Cardiac Glycosides / Q000378:metabolism*; D005260:Female; D006801:Humans; D006973:Hypertension / Q000201:enzymology* / Q000503:physiopathology; D008861:Microsomes / Q000201:enzymology / Q000378:metabolism; D010042:Ouabain / Q000378:metabolism; D010920:Placenta / Q000201:enzymology* / Q000378:metabolism* / Q000648:ultrastructure; D011247:Pregnancy; D011249:Pregnancy Complications, Cardiovascular / Q000201:enzymology / Q000378:metabolism / Q000503:physiopathology
D002301:Cardiac Glycosides; D010042:Ouabain