Tryptophan degradation and indoleamine 2,3-dioxygenase in MRC-5 fibroblasts

Abstract

T h e present study demonstrates and confirms the dependence o f the enterotoxin o n Ca'+ for induction o f effects on Vcro cells. l h e chemicals that interfered with the enterotoxin action, mediate their action through Ca? + transport and metabolism. T h e ability of Neutral Red to inhibit the enterotoxin action could be linked to the ability of this chemical to block cation transport (Barbosa & Peters, 197 1). Protective action observed with propranolol ( a P-adrenergic blocker) and lanthanum chloride (a specific antagonist o f Ca is probably due t o thc ability of these chemicals to block potential Ca2+ channels (Suzuki et al., 1986) and to depress Ca'+ATPase activity, respectively. Therefore, it seems that inhibition of the active Ca'+ transport plays a crucial role in preventing enterotoxin action. Furthermore, results obtained with Ruthenium Red, a specific inhibitor of C a ? + uptake across the inner membrane of the mitochondria (Denton et ul., 1980; Marshall et al., 1984). suggest that mitochondria may be involved in the action of the enterotoxin.