KININS STIMULATE NET CHLORIDE SECRETION BY THE RAT COLON
- 1Short circuit current (SCC), transepithelial conductance and ion fluxes were measured across the isolated descending colon of the rat in response to bradykinin or kallidin.
- 2Kinins added to the serosal bath caused immediate increases in SCC but were ineffective when added to the mucosal bath. Increases in SCC were accompanied by significant increases in transepithelial conductance. Threshold kinin concentration was 0.5 nm and maximal increases were seen at 50–100 nm.
- 3A rat glandular kallikrein (7 nm) or mellitin (2 μm) also increased SCC if added to the serosal bath.
- 4Responses to kinins were unaffected by mucosal amiloride (100 μm) but attenuated or blocked by serosal frusemide (100 μm), indomethacin (1 μm) or mepacrine (50 μm).
- 5Replacement of chloride ion in the serosal bath by gluconate and sulphate ions abolished responses to kinins which reappeared after chloride re-addition.
- 6Measurement of 36Cl, 22Na and 86Rb fluxes across the tissue showed that the kinin-induced increase in SCC resulted principally from increased net chloride secretion. Effects upon 22Na or 86Rb flux were minimal and made no contribution to the current responses observed in this tissue.
- 7The results prove that kinins stimulate net chloride secretion in the rat colon, most probably via a prostaglandin-dependent pathway.