Electric potential of contractile vacuole lumen relative to the cytosol

Range ~80 mV
Organism Protozoan Paramecium multimicronucleatum
Reference Raven JA, Doblin MA. Active water transport in unicellular algae: where, why, and how. J Exp Bot. 2014 Dec65(22):6279-92. doi: 10.1093/jxb/eru360. p.6284 left column top paragraphPubMed ID25205578
Primary Source Grønlien HK, Stock C, Aihara MS, Allen RD, Naitoh Y. Relationship between the membrane potential of the contractile vacuole complex and its osmoregulatory activity in Paramecium multimicronucleatum. J Exp Biol. 2002 Oct205(Pt 20):3261-70.PubMed ID12235204
Method Primary source abstract: "The electric potential of the contractile vacuole (CV) of Paramecium multimicronucleatum was measured in situ using microelectrodes, one placed in the CV and the other (reference electrode) in the cytosol of a living cell. The CV potential in a mechanically compressed cell increased in a stepwise manner to a maximal value (approximately 80 mV) early in the fluid-filling phase."
Comments P.6284 left column top paragraph: "There is evidence of carbonic anhydrase in the contractile vacuole, with slowing of the water inflow–outflow cycle when the activity is inhibited (Marchesini et al., 2002 fig. 3 of Docampo et al., 2013). However, there are other reasons why the contractile vacuole lumen does not acidify despite the operation of the proton V-ATPase. The contractile vacuole lumen is ~80 mV positive relative to the cytosol (primary source), so there is an inside positive electrochemical potential difference for protons across the contractile vacuole membrane so electrically driven ion fluxes and secondary active transport processes with protons as the driving ion could still occur across the membrane despite the absence of a pH difference."
Entered by Uri M
ID 112731