Robert Rakowski

Professor, Department Chair
Department of Biological Sciences
phone: 740-593-2290
fax: 740-593-0300
office: Irvine Hall 106
rakowski@ohio.edu

Research Summary

My research is directed towards understanding the biophysical basis of cellular functions. There are currently two lines of research being conducted in my laboratory: 1) voltage-clamp studies of Na+/K+ pump current and flux in internally-dialyzed squid giant axons and 2) studies of ionic channels and pumps in Xenopus oocytes and barnacle muscle fibers. During May and June I conduct research at the Marine Biological Laboratory in Woods Hole, Massachusetts on the NA+/K+ pump in squid giant axons. We have developed a new technique that permits the direct measurement of electrogenic pump current and the measurement of tracer fluxes of Na+ and K+. Both the internal and external solution composition can be manipulated and the cell membrane potential clamped at any desired level. We have been able to reverse the Na+/K+ pump by steepening the electrochemical gradients for Na+ and K+ and depleting the intracellular ATP concentration. The pump continues to be electrogenic when operating in the reverse mode. We have also investigated the voltage-dependence and stoichiometry of forward pump operation. These studies are directed at obtaining a molecular-level understanding of the individual kinetic steps during active transport of Na+ and K+. In Athens, my research is focused on transport studies in Xenopus oocytes. We are investigating the effects of changes in substrate concentration on the voltage dependence of the Na+/K+ pump in Xenopus oocytes and are also measuring transient pump currents (pump gating currents) using the cut-open oocyte voltage clamp technique.

Selective References

• Sagar, A. and Rakowski, R.F. Access channel model for the voltage dependence of the forward-running Na+/K+ pump. J. Gen. Physiol. 103:869-894, 1994.
  
  
• Holmgren, M. and Rakowski, R.F. Pre-steady-state transient currents mediated by the Na/K pump in internally perfused Xenopus oocytes. Biophys. J. 66:912-922, 1994.
  
  
• Holmgren, M., Wagg, J., Bezanilla, F., Rakowski, R., De Weer, P., and Gadsby, D. Three distinct and sequential steps in the
  release of sodium ions by the Na./K-ATPase. Nature 403:898-901, 2000.