ABSTRACT
The extracellular disulfide reductase, if it exists as a discrete enzyme system or redox chain that demonstrates hysteresis, should have both immediate effects and generate long-term synthetic changes. The question arises as to whether the extracellular disulfide reductase, besides being sensitive to mitogens and antioxidants, can respond to physical stressors and microenvironmental changes. A novel location and means of transferring extracellular disulfide reductase has been suggested by the thioredoxin interaction with the Interleukin-2 (IL-2) receptor and the disulfide isomerase activity of follitropin and lutropin. The concept of an extracellular disulfide reductase arose with the feeder cell phenomenon in which macrophages provide growth support for primary or cytokine-dependent lymphoid cells. Although reduced glutathione is the principal source of thiols and reducing equivalents from thiols for detoxification and normal cellular growth, it is inadequate as a source of extracellular disulfide reductase because few cells export it as a thiol.
