Differential activation of the HCO(3)(-) conductance through the cystic fibrosis transmembrane conductance regulator anion channel by genistein and forskolin in murine duodenum.
OBJECTIVE
Many cystic fibrosis (CF)-associated mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) anion channels affect CFTR-activated HCO(3)(-) transport more than Cl(-) transport. Targeting the CFTR HCO(3)(-) conductance, if possible, may therefore be of major therapeutic benefit. In the present study, we examined the effects of genistein and forskolin on duodenal mucosal HCO(3)(-) and Cl(-) secretion.


METHODS
Murine duodenal mucosal HCO(3)(-) and Cl(-) secretions were examined in vitro in Ussing chambers by the pH stat and short circuit current (I(sc)) techniques.


RESULTS
Genistein markedly stimulated duodenal HCO(3)(-) secretion and I(sc) in a dose-dependent manner in CFTR wild-type mice, but not in CFTR null mice. CFTR(inh)-172, a highly specific CFTR inhibitor, inhibited genistein-stimulated duodenal HCO(3)(-) secretion and I(sc) in wild-type mice. Genistein induced 59% net HCO(3)(-) increase and 123% net I(sc) increase over basal value, whereas forskolin, an activator of adenylate cyclase, induced 94% net HCO(3)(-) increase and 507% net I(sc) increase, indicating that, compared with forskolin, genistein induced a relatively high HCO(3)(-)/I(sc) ratio. Further data showed that CFTR HCO(3)(-)/Cl(-) conductance ratio was 1.05 after genistein stimulation, whereas after forskolin stimulation, the CFTR HCO(3)(-)/Cl(-) conductance ratio was 0.27.


CONCLUSIONS
Genistein stimulates duodenal HCO(3)(-) and Cl(-) secretion through CFTR, and has a relatively high selectivity for the CFTR HCO(3)(-) conductance, compared with forskolin. This may indicate the feasibility of selective targeting of the HCO(3)(-) conductance of the CFTR channels.
Tuo
Biguang
B
Department of Gastroenterology, Affiliated Hospital, Zunyi Medical College, Zunyi, China. tuobiguang@yahoo.com.cn
Wen
Guorong
G
Seidler
Ursula
U
D000818:Animals; D000838:Anions; D001639:Bicarbonates / Q000378:metabolism*; D002712:Chlorides / Q000378:metabolism; D005576:Colforsin / Q000494:pharmacology*; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000819:agonists / Q000235:genetics / Q000502:physiology*; D004386:Duodenum / Q000187:drug effects* / Q000378:metabolism; D019833:Genistein / Q000494:pharmacology*; D066298:In Vitro Techniques; D007413:Intestinal Mucosa / Q000187:drug effects* / Q000378:metabolism; D017136:Ion Transport; D051379:Mice; D018345:Mice, Knockout; D009154:Mutation
D000838:Anions; D001639:Bicarbonates; D002712:Chlorides; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D005576:Colforsin; D019833:Genistein