A simple method for obtaining functionally and morphologically intact primary cultures of the medullary thick ascending limb of Henle's loop (MTAL) from rabbit kidneys

. We describe a simple method for obtaining functionally and morphologically intact primary cultures of cells from the medullary thick ascending limb of rabbit kidneys. After digesting dissected fragments of the inner stripe of the outer medulla with collagenase, a suspension of tubule fragments is obtained, the vast majority of which are medullary thick ascending limb (MTAL) segments. These are identified individually by their morphological appearance and large amounts are collected with a micropipette mounted on a micromanipulator. This ensures maximal homogeneity of the starting material. Monolayers of cells grow out of these MTAL segments after seeding them onto collagen-coated, permeable filter supports. During the week following confluence, the cultures exhibit an apical side-positive transepithelial potential difference. Electron microscopic examination shows a monolayer of polarised cells with characteristics of distal tubular cells. The primary cultures express Tamm-Horsfall protein at their apical surface. Additional evidence for their differentiation and polarisation is the net ammonium influx, which occurs at very high rates across the apical membrane and is much slower across the basolateral membrane, as judged by measurements of intracellular pH. Adenosine 3′,5′-cyclic monophosphate (cAMP) production is stimulated by arginine-vasopressin, calcitonin or isoproterenol (all 1 µmol/l). Intracellular calcium signalling is observed after stimulation with 1 µmol/l adenosine, adenosine 5′-triphosphate (ATP) and bradykinin. In addition, we compared these characteristics with those of TALH-SVE cell monolayers, an established immortalised cell line of the same origin.