Topological relationships between porcine anterior pituitary hormones and the thioredoxin and glutaredoxin systems

Thioredoxin (TRX) and glutaredoxin (GRX) had previously been localized in folliculo-stellatae (FS) cells and in only a fraction of glandular cells of the anterior pituitary (Padilla et al., 1992). Here we report on a double immunolabelling study carried out to determine the correlation between the type of secretory cell and the presence of TRX or GRX. TRX and GRX levels were under the detection limits in gonadotropes, thyrotropes and corticotropes. A considerable proportion of lactotropes contained TRX or GRX; a higher proportion of somatotropes contained TRX and all of them were GRX-positive. The secretory cell types more frequently detected in the epithelium of well-defined follicles lined by TRX-positive FS cells were somatotropes and lactotropes followed by corticotropes; gonadotropes and thyrotropes were scarce in these structures. Regarding the biological functions of glutaredoxin and thioredoxin, these results show that involvement in the processing of secretory proteins is not a general property of these two thiol-disulfide oxidoreductases, not even specifically in the case of cysteine-rich secretory proteins. On the other hand, another type of functional specificity perhaps related to the heterogeneous response of the endocrine cells is discussed.