K+-dependent 3-O-methylfluorescein phosphatase activity in crude homogenate of rodent heart ventricle: effect of K+ depletion and changes in thyroid status.
The total Na+-K+-ATPase activity in rodent heart ventricle was quantified by determination of K+-dependent, ouabain suppressible 3-O-methylfluorescein phosphatase activity. A K+-dependent phosphatase activity of 0.80 mumol/min per g wet wt was obtained from crude homogenate of heart ventricle from 4-week-old guinea pigs. The anticipated association between K+-dependent phosphatase activity and Na+-K+-activated ATP hydrolysis could be clearly demonstrated in the crude homogenate. Based upon a molecular activity of 550/min the corresponding cardiac glycoside receptor concentration in the crude homogenate was 1450 pmol/g wet wt. In crude homogenate of heart ventricle from 3-month-old rats the K+-dependent phosphatase activity was 1.16 mumol/min per g wet wt. Following 4 weeks of K+ depletion of the rats, a decrease of 13% in total K+ content of the heart ventricle was seen. This was associated with a 14% decrease in K+-dependent phosphatase activity. The induction of hypo- and hyperthyroidism for 3 weeks in rats was followed by a decrease of 27% and an increase of 13% in K+-dependent phosphatase activity, respectively.
D000818:Animals; D001921:Brain / Q000201:enzymology; D005260:Female; D005452:Fluoresceins / Q000378:metabolism*; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007668:Kidney / Q000201:enzymology; D007700:Kinetics; D009206:Myocardium / Q000201:enzymology*; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D013961:Thyroid Gland / Q000502:physiology*
C032079:3-O-methylfluorescein phosphate; D005452:Fluoresceins; D010042:Ouabain; C045349:3-O-methyl-fluorescein phosphatase; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium