Effects of ouabain on proliferation of human endothelial cells correlate with [Na.sup.+], [K.sup.+]-ATPase activity and intracellular ratio of [Na.sup.+] and [K.sup.+]

• Published in: Biochemistry (Moscow) 2016-08, Vol.81 (8), p.876
• Main Authors: Tverskoi, A.M, Sidorenko, S.V, Klimanova, E.A, Akimova, O.A, Smolyaninova, L.V, Lopina, O.D, Orlov, S.N
• Format: Article
• Language: English
• Subjects: ATPases; Cell proliferation; Health aspects; Ouabain
• ISSN: 0006-2979
• DOI: 10.1134/S0006297916080083

Side-by-side with inhibition of the [Na.sup.+],[K.sup.+]-ATPase ouabain and other cardiotonic steroids (CTS) can affect cell functions by mechanisms other than regulation of the intracellular [Na.sup.+] and [K.sup.+] ratio ([[[Na.sup.+]].sub.i]/[[[K.sup.+]].sub.i]). Thus, we compared the dose- and time-dependences of the effect of ouabain on intracellular [[[Na.sup.+]].sub.i]/[[[K.sup.+]].sub.i] ratio, [Na.sup.+],[K.sup.+]-ATPase activity, and proliferation of human umbilical vein endothelial cells (HUVEC). Treatment of the cells with 1-3 nM ouabain for 24-72 h decreased the [[[Na.sup.+]].sub.i]/[[[K.sup.+]].sub.i] ratio and increased cell proliferation by 20-50%. We discovered that the same ouabain concentrations increased [Na.sup.+],[K.sup.+]-ATPase activity by 25-30%, as measured by the rate of [sup.86][Rb.sup.+] influx. Higher ouabain concentrations inhibited [Na.sup.+],[K.sup.+]-ATPase, increased [[[Na.sup.+]].sub.i]/[[[K.sup.+]].sub.i] ratio, suppressed cell growth, and caused cell death. When cells were treated with low ouabain concentrations for 48 or 72 h, a negative correlation between [[[Na.sup.+]].sub.i]/[[[K.sup.+]].sub.i] ratio and cell growth activation was observed. In cells treated with high ouabain concentrations for 24 h, the [[[Na.sup.+]].sub.i]/[[[K.sup.+]].sub.i] ratio correlated positively with proliferation inhibition. These data demonstrate that inhibition of HUVEC proliferation at high CTS concentrations correlates with dissipation of the [Na.sup.+] and [K.sup.+] concentration gradients, whereas cell growth stimulation by low CTS doses results from activation of [Na.sup.+],[K.sup.+]-ATPase and decrease in the [[[Na.sup.+]].sub.i]/[[[K.sup.+]].sub.i] ratio. DOI: 10.1134/S0006297916080083 Key words: proliferation, endothelium, [Na.sup.+],[K.sup.+]-ATPase, ouabain, intracellular [Na.sup.+] and [K.sup.+]