EHRLICH CELL PLASMA-MEMBRANE REDOX SYSTEM IS MODULATED THROUGH SIGNAL-TRANSDUCTION PATHWAYS INVOLVING CGMP AND CA2+ AS 2ND MESSENGERS

Ehrlich cell plasma membrane ferricyanide reductase activity increased in the presence of mastoparan, a generic activator of G proteins, usi ng either whole cells or isolated plasma membrane fractions. Agents th at increase intracellular cAMP also increased the rate of ferricyanide reduction by Ehrlich cells. For the first time, evidence is shown on a modulation of plasma membrane redox system by cGMP. In fact, permean t analogs of cGMP, dibutyryl cGMP, and 8-bromo-cGMP increased the rate of ferricyanide reduction by the Ehrlich cell plasma membrane redox s ystem. Furthermore, specific inhibition of cGMP-phosphodiesterases by dipyridamole was also accompanied by an enhancement in the rate of fer ricyanide reduction. On the other hand, treatments expected to increas e cytoplasmic Ca2+ concentrations were accompanied by a remarkable sti mulation of the reductase activity. Taking all these data together, it seems that the Ehrlich cell plasma membrane redox system is under a m ultiple and complex regulation by different signal transduction pathwa ys involving G proteins, cyclic nucleotides, and Ca2+ ions.