CHLORIDE TRANSPORT IN PRIMARY CULTURES OF RABBIT COLONOCYTES AT DIFFERENT STAGES OF DEVELOPMENT

Background & Aims: Ontogeny of colonic Cl- transport and its regulatio n has been characterized inadequately. The aim of this report was to s tudy developmental changes in Cl- transport in primary cultures of rab bit distal colonocytes. Methods: Colonocytes from newborn (7-9 days ol d), weanling (25-28 days old), and adult (6 months old) rabbits were c ultured for 24 hours on a collagen IV matrix, and Cl- transport was me asured using the fluoroprobe 6-methoxyquinolyl acetoethyl ester. Resul ts: Cl- permeabilities were dependent on [Cl-](o) with maximal rates ( in millimoles per liter per second) at [Cl-](o) = 75 mmol/L (newborns; 0.15 +/- 0.04; weanlings; 0.2 +/- 0.02; and adults, 0.32 +/- 0.06). I nflux was inhibited significantly by the Cl- channel (50 mu mol/L diph enylamine-2-carboxylate) and the Na+-K+-2Cl(-) cotransport (10 mu mol/ L furosemide) inhibitors. The adenosine 3',5'-cyclic monophosphate (cA MP)-dependent secretagogues, prostaglandin E(1) (1 mu mol/L), forskoli n (1 mu mol/L), and 8-bromo-cAMP (100 mu mol/L), and the protein kinas e 6 activator, phorbol 12-13 dibutyrate (1 mu mol/L), increased Cl- in flux significantly in all groups with adults showing greatest stimulat ion. However, taurodeoxycholate (0.025-1 mmol/L) had an effect only in the adult and the guanosine 3',5'-cyclic monophosphate (cGMP) activat ors STa and 8-bromo-cGMP had no effect. Conclusions: Rabbit distal col onocytes possess inhibitor-sensitive Cl- permeabilities even in neonat es. However, the ontogeny of their regulation depends on the secretago gue-signaling pathway.