Venosa R A
Centro de Investigaciones Cardiovasculares, Facultad de Ciencias Médicas de la Universidad Nacional de La Plata, La Plata, Argentina.
Acta Physiol Scand. 2005 Dec;185(4):329-34. doi: 10.1111/j.1365-201X.2005.01493.x.
The activation of both protein kinases A (PKA) and protein kinases C (PKC) in some cell types increases and in others reduces active Na+ efflux. These effects have been ascribed to either a change in the rate of ionic translocation by a fixed number of Na+ pumps or, a change in the number of plasma membrane pumps. The purpose of the present experiments was to study the effect of activating PKA and PKC on the Na+ extrusion by the Na+ pump in frog skeletal muscle.
Na+ (22Na+) fluxes and ouabain (3H-ouabain) binding were measured in frog sartorius muscles.
Both activation of PKA and PKC increased the active Na+ extrusion by a factor of two; these effects were not additive. Ouabain binding experiments indicated that the pump stimulation by activation of these kinases is not associated with any significant increase in the number of plasma membrane pumps. Stimulation of the active Na+ efflux by protein kinase activation (no change in the number of sarcolemmal pumps) and by hypotonicity (increase in the number of pumps) could be elicited in the same preparation and they were additive.
It is concluded that in frog skeletal muscle fibres, (1) activation of both PKA and PKC stimulate the Na+ pump by increasing its rate of ionic translocation; and (2) two modes of Na+ active transport (with and without an increase in the number of pumps) are operative, and can be at work simultaneously, a phenomenon to be reckoned with.
在某些细胞类型中，蛋白激酶A（PKA）和蛋白激酶C（PKC）的激活会增加，而在其他细胞类型中则会降低活性钠外流。这些效应被归因于固定数量的钠泵离子转运速率的变化，或者质膜泵数量的变化。本实验的目的是研究激活PKA和PKC对青蛙骨骼肌中钠泵钠排出的影响。
在青蛙缝匠肌中测量钠（²²Na⁺）通量和哇巴因（³H-哇巴因）结合。
PKA和PKC的激活均使活性钠排出增加了两倍；这些效应不是相加的。哇巴因结合实验表明，通过激活这些激酶对泵的刺激与质膜泵数量的任何显著增加无关。在同一标本中可以引发蛋白激酶激活（肌膜泵数量无变化）和低渗（泵数量增加）对活性钠外流的刺激，且它们是相加的。
得出结论，在青蛙骨骼肌纤维中，（1）PKA和PKC的激活均通过增加钠泵的离子转运速率来刺激钠泵；（2）存在两种钠主动转运模式（泵数量增加和不增加），并且可以同时起作用，这是一个需要考虑的现象。
