Bipolar Secretion of Androgen-Binding Protein and Transferrin by Sertoli Cells Cultured in a Two-Compartment Culture Chamber*

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Abstract
The influence of various medium supplements on Sertoli cell (Sc) monlayer permeability to [3H]inulin and polarized secetion of transferrin (Trf) and androgen-binding protein (ABP) was investigated in a two-compartment culture chamber. Sc from 140 and 18-day-old rats were maintained for 13 days in one of the following media: 1) Modified Eagle''s Medium-Ham''s F-12 (DFM), 2) DFM plus insulin, epidermal growth factor, progesterone, hydrocortisone, and vitamins A and E (6F), 3) 6F plus testosterone (7F), 4) 7F plus FSH (8F), 5) 6F plus 2% fetal bovine serum (6F2S), 6F plus 5% fetal bovine serum (6F5S). The monolayer permeability to [3H]inulin decreased rapidly during the initial 3-5 days of cuture for the Sc isolated from 18- and 14-day-old animals, then remained stable in all media except DFM. Morphological examination revealed the presence of tight junctions between neighbouring Sc in both age groups, indicating their de novo formation. Secretion of Trf was lost in DFM and steadily declined. In all other media, Trf secretion peaked on day 5 and remained relatively constant after day 7. Medium 7F only slightly and inconsistently increased the secretion, whereas 8F was always highly stimulatory compared to 6F. Supplementation of 6F with serum resulted in the greatest Trf secretion. In the case of ABP, three different secretion patterns were noted depending on the medium composition; secretion was greatest in the presence of 5% fetal bovine serum. The medium supplements also differentially affected the polarity of Trf and ABP secretion. The ratio of Trf secreted to the outer and inner compartments (OC/IC) was approximately 2.0 in DFM and was not influenced by supplements in 6F, 7F, and 8F. However, in serum-containing media, the OC/OC ratio gradually increased with time to about 5.0 on day 13. The average OC/IC ratio of ABP was 1.7 in DFM and, in contrast to Trf, declined to 0.7 in other serum-free media. Serum supplementation reversed and increased the ABP ratio to about 6.0 on day 13. These data indicate that Sc grown on permeable supports form confluent monolayers that limit the diffusion of macromolecules, most likely due to the formation of tight junctions. The monolayer pemeability as well as the total and polarized secretion of Trf and ABP are differentially regulated by hormones and serum factors.