Influence of Rete Testis Fluid on the Metabolism of Testosterone by Cultured Principal Cells Isolated from the Proximal or Distal Caput of the Rat Epididymis

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Abstract
Principle cells from 120 elutriations were used to improve procedures for culturing cells from the proximal or distal caput epididymidis. The criteria evaluated were metabolism of testosterone (T) to 5 alpha-reduced metabolites and cellular morphology after 6 days of culture. Isolated principal cells (greater than 90% viability) were cultured at 34 degrees C within a floating collagen matrix. Inclusion of transferrin or retinol in the culture medium increased the production of 5 alpha-reduced metabolites. Aggregation of principal cells before entrapment in the collagen matrix resulted in higher production of 5 alpha-reduced metabolites and more cells with a normal find structure than entrapment of dispersed cells in the matrix. Aggregated cells tended to form sheets or clusters, frequently arranged around a central lumen, with junctional complexes between adjacent cells. Cell polarity and morphologic features distinguishing principal cells from the proximal caput and distal caput epididymidis were retained. An average of 91% of the cells in aggregates were morphologically normal on Day 6 of culture in contrast to 5% for the single cells. Utilizing the improved culture procedure, we tested the hypothesis that ovine rete testis fluid (RTF) contains macromolecules which would aid in maintenance of a high rate of T metabolism. Principal cells were cultured in medium supplemented with 0 or 10% RTF, 10% ultrafiltrate of RTF (less than 10,000 daltons), or 10% newborn calf serum (NCS). Conversion of [3H]T to 5 alpha-reduced metabolites by cells from the proximal caput was twice that in cells from the distal caput on Day 6 of culture. Inclusion in the culture medium of 10% RTF or 10% NCS, but not 10% ultrafiltrate of RTF, increased (P less than 0.05) the production of 5 alpha-reduced metabolites by cells from both regions. We conclude that macromolecules in RTF or NCS are beneficial to maintenance of the ability to metabolize T by cultured principal cells, especially those from the proximal caput.