Use of a prostaglandin compound as shown by the following general formula: wherein L, M and N are hydrogen atom, hydroxy, halogen atom, lower alkyl, hydroxy (lower) alkyl, or oxo, wherein at least one of L and M is a group other than hydrogen, and the five-membered ring may have at least one double bond; A is -CH 2 OH, -COCH 2 OH -COOH or a functional derivative thereof; B is -CH 2 -CH 2 -, -CH=CH- or -C≡C-; Z is wherein R 4 and R 5 are hydrogen, hydroxy, halogen, lower alkyl, lower alkoxy or hydroxy (lower) alkyl, wherein R 4 and R 5 are not hydroxy and lower alkoxy at the same time; R 1 is a saturated or unsaturated bivalent lower or medium aliphatic hydrocarbon residue, which is unsubstituted or substituted with halogen, alkyl, hydroxy, oxo, aryl or heterocyclic group, and at least one of carbon atom in the aliphatic hydrocarbon is optionally substituted by oxygen, nitrogen or sulfur; and Ra is a saturated or unsaturated lower or medium aliphatic hydrocarbon residue, which is unsubstituted or substituted with halogen, oxo, hydroxy, lower alkoxy, lower alkanoyloxy, cyclo(lower)alkyl, cyclo(lower)alkyloxy, aryl, aryloxy, heterocyclic group or hetrocyclic-oxy group; cyclo(lower)alkyl; cyclo(lower)alkyloxy; aryl; aryloxy; heterocyclic group; heterocyclic-oxy group; wherein lower alkyl refers to group having up to 6 carbon atoms,lower or medium aliphatic hydrocarbon refers to a straight or branched hydrocarbon group having 1-14 carbon atoms; for manufacturing a pharmaceutical composition for treating a condition associated with reduced chloride ion permeability in a mammalian subject by opening ClC channels, wherein said condition is selected from the group consisting of myotonia atrophica, calculus renum, anxiety, insomnia, cystic fibrosis, epilepsia, anesthesia, neuropathy, congenital myotonia, hereditary nephrolithiasis and hypercalciuria. wherein L, M and N are hydrogen atom, hydroxy, halogen atom, lower alkyl, hydroxy (lower) alkyl, or oxo, wherein at least one of L and M is a group other than hydrogen, and the five-membered ring may have at least one double bond; A is -CH 2 OH, -COCH 2 OH -COOH or a functional derivative thereof; B is -CH 2 -CH 2 -, -CH=CH- or -C≡C-; Z is wherein R 4 and R 5 are hydrogen, hydroxy, halogen, lower alkyl, lower alkoxy or hydroxy (lower) alkyl, wherein R 4 and R 5 are not hydroxy and lower alkoxy at the same time; R 1 is a saturated or unsaturated bivalent lower or medium aliphatic hydrocarbon residue, which is unsubstituted or substituted with halogen, alkyl, hydroxy, oxo, aryl or heterocyclic group, and at least one of carbon atom in the aliphatic hydrocarbon is optionally substituted by oxygen, nitrogen or sulfur; and Ra is a saturated or unsaturated lower or medium aliphatic hydrocarbon residue, which is unsubstituted or substituted with halogen, oxo, hydroxy, lower alkoxy, lower alkanoyloxy, cyclo(lower)alkyl, cyclo(lower)alkyloxy, aryl, aryloxy, heterocyclic group or hetrocyclic-oxy group; cyclo(lower)alkyl; cyclo(lower)alkyloxy; aryl; aryloxy; heterocyclic group; heterocyclic-oxy group; wherein lower alkyl refers to group having up to 6 carbon atoms,lower or medium aliphatic hydrocarbon refers to a straight or branched hydrocarbon group having 1-14 carbon atoms; for manufacturing a pharmaceutical composition for treating a condition associated with reduced chloride ion permeability in a mammalian subject by opening ClC channels, wherein said condition is selected from the group consisting of myotonia atrophica, calculus renum, anxiety, insomnia, cystic fibrosis, epilepsia, anesthesia, neuropathy, congenital myotonia, hereditary nephrolithiasis and hypercalciuria.