Prostaglandin synthesis by isolated cells from the outer medulla and from the thick ascending loop of Henle of rabbit kidney

Prostaglandins (PGs) synthesized in the medulla, a major source of renal PGs, could have a direct effect on several tubular functions. In order to better characterize the site and pattern of PG synthesis in different medullary nephron segments, we examined PG synthesis by isolated medullary cells, a preparation enriched in medullary collecting tubule cells and isolated cells from the thick ascending limb of Henle's loop (TALH). Incubation of medullary cells and medullary collecting tubule cells in the presence of 5 μM [¹⁴C]arachidonic acid produced predominantly PGE₂ with much less PGF₂(α). In comparison, TALH cells synthesized only about 20% as much labeled PG composed of nearly equal amounts of PGE₂ and PGF₂(α). Specific radioimmunoassay after incubation in the absence of exogenous arachidonic acid revealed that medullary cells synthesized 83 ± 15 ng of PGE₂/mg of protein x 15 min compared with 15 ± 5 ng of PGE₂ for TALH cells. Furosemide (1 mM) inhibited PGE₂ synthesis in medullary cells but had no effect on TALH cells. Bumetanide (1 mM) and amiloride (1 mM) had no effect. The calcium ionophore A23187 (2 μM) doubled PGE₂ synthesis in both cell populations. The synthesis of PGF₂(α) was comparable in all three preparations, but was only 5% of PGE₂ production in medullary and medullary collecting tubule cells and about 20% of PGE₂ production in TALH cells. Furosemide (1 mM) stimulated PGF₂(α) synthesis in medullary cells and TALH cells (2.9 ± 0.7 to 6.8 ± 1.3 and 1.5 ± 0.7 to 5.5 ± 1.4 ng/mg of protein x 15 min, respectively). Hydrochlorothiazide was without effect. A23187 (2 μM) increased PGF₂(α) synthesis 2- to 3-fold in both cell populations. These results indicate that cells from different nephron segments have different patterns of PG synthesis. They do not support a direct role for PGs in the action of loop diuretics, but do not rule out possible modulation of NaCl transport by PGs.