Similarities of the in vivo and in vitro effects of mercuric chloride on [3H]ouabain binding and potassium activation of Na+/K(+)-ATPase in isolated rat cerebral microvessels.
A previous study revealed that a single i.p. administration of 6 mg/kg body wt. of mercuric chloride (MC) durably inhibits the rat cerebral microvascular Na+/K(+)-ATPase activity [1]. In this study, cerebral microvessels isolated 18 h after MC treatment were compared to those obtained from control rats and subsequently treated or not treated with MC in vitro, with regard to: (a) [3H]ouabain binding to, and (b) K(+)-activation kinetics of, the Na+/K(+)-ATPase. Microvessels from MC-treated rats showed a decrease of [3H]ouabain binding down to 62% of the control binding, and the same degree of inhibition was attained in microvessels treated in vitro with 5 microM MC. Analysis of the K(+)-activation kinetics of Na+/K(+)-ATPase revealed a decrease of Vmax from the control value of 13.1 to 7.67 mumol/mg/h in microvessels from MC-treated rats and 6.07 mumol/mg/h in microvessels treated in vitro with 5 microM MC, with no change in Km in either case. The similarity of the effects of in vivo and in vitro treatments suggests that the inhibition of the cerebromicrovascular Na+/K(+)-ATPase following in vivo administration of MC results from a direct interaction of Hg2+ with the enzyme.
Albrecht
J
J
Department of Neuropathology, Medical Research Centre, Polish Academy of Sciences, Warsaw.
Hilgier
W
W
D000818:Animals; D046508:Culture Techniques; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D005625:Frontal Lobe / Q000098:blood supply* / Q000187:drug effects; D007274:Injections, Intraperitoneal; D008297:Male; D008627:Mercuric Chloride / Q000008:administration & dosage / Q000633:toxicity*; D008833:Microcirculation / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D010042:Ouabain / Q000378:metabolism*; D011188:Potassium / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
D008627:Mercuric Chloride; D010042:Ouabain; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium