Cell–cell Interaction Underlies Formation of Fluid in the Male Reproductive Tract of the Rat

The epithelia lining the epididymides of many species consists of several cell types. We have provided evidence that the basal cells are essential to the integrated functions of the epithelium. Basal cells, but not principal cells, and other cells in the epididymis express TRPC3 and COX-1. We have isolated basal cells from intact rat epididymis using antibody-coated Dynabeads and subjected them to whole-cell patch-clamp measurement of nonselective cation channel activity, a feature of TRPC3 protein, and Fluo-3 fluorescence measurement of intracellular Ca²⁺ concentration. The results show that a nonselective cation current blockable by La³⁺ (0.1 mM), Gd³⁺ (0.1 mM), or SKF96365 (20 μM) could be activated by lysylbradykinin (200 nM). In cells loaded with Fluo-3, addition of lysylbradykinin (100 nM) caused a sustained increase of intracellular Ca²⁺. This effect was blocked by Gd³⁺ (0.1 mM) or SKF96365 (20 μM) and was not observed in Fluo-3–loaded principal cells. Stimulation of basal cell/principal cell cocultures with lysylbradykinin (200 nM) evoked in principal cells a current with CFTR-Cl⁻ channel characteristics. Isolated principal cells in the absence of basal cells did not respond to lysylbradykinin but responded to PGE₂ (100 nM) with activation of a CFTR-like current. Basal cells, but not principal cells, released prostaglandin E₂ when stimulated with lysylbradykinin (100 nM). The release was blocked by SKF96365 (20 μM) and BAPTA-AM (0.05 or 0.1 mM). Confluent cell monolayers harvested from a mixture of disaggregated principal cells and basal cells responded to lysylbradykinin (100 nM) and PGE₂ (500 nM) with an increase in electrogenic anion secretion. The former response was dependent on prostaglandin synthesis as piroxicam blocked the response. However, cell cultures obtained from principal cells alone responded to PGE₂ but not to bradykinin. These results support the notion that basal cells regulate principal cells through a Ca²⁺ and COX signaling pathway.