Na,K-ATPase from placenta of women with pregnancy-induced hypertension exhibits an increased affinity for cardiac glycosides.
Microsomes were prepared from placentas of normotensive women and of patients suffering from pregnancy-induced hypertension (PIH). Activity of Na,K-ATPase (estimated as ATP hydrolysis) from the hypertensive tissue was lower than from tissue of normotensive women, even if the number of Na,K-ATPase molecules (monitored by anthroyl ouabain binding) was actually greater in the hypertensive tissue. The affinity of Na,K-ATPase for anthroyl ouabain was about four times higher in plasma membranes of hypertensives, indicating some structural change in the Na,K-ATPase or in its vicinity. Assuming the presence of an endogenous digitalis-like factor, the results suggest a simple way of explaining not only the lower Na,K-ATPase activity in the placental membranes of hypertensives but also the different extent of enzyme inhibition in different tissues of PIH patients.
Amler
E
E
Institute of Physiology, Academy of Sciences of the Czech Republic, Prague.
Cester
N
N
Magnanelli
R
R
Mazzanti
L
L
Kotyk
A
A
Romanini
C
C
D000873:Anthracenes / Q000378:metabolism; D002301:Cardiac Glycosides / Q000378:metabolism*; D005260:Female; D005456:Fluorescent Dyes; D006801:Humans; D006973:Hypertension / Q000201:enzymology*; D066298:In Vitro Techniques; D008566:Membranes / Q000201:enzymology / Q000378:metabolism; D008861:Microsomes / Q000201:enzymology / Q000378:metabolism; D010042:Ouabain / Q000031:analogs & derivatives / Q000378:metabolism; D010920:Placenta / Q000201:enzymology*; D011247:Pregnancy; D011249:Pregnancy Complications, Cardiovascular / Q000201:enzymology*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
D000873:Anthracenes; D002301:Cardiac Glycosides; D005456:Fluorescent Dyes; D010042:Ouabain; C013814:anthroylouabain; D000254:Sodium-Potassium-Exchanging ATPase