Submitted on April 3, 2009
Revised on May 22, 2009
Accepted on June 15, 2009
Genistein stimulates electrogenic Cl- secretion via phosphodiesterase modulation in the mouse jejunum
Pin-Chun Chao1 and Kirk L. Hamilton2*
1 University of Otago School of Medicine
2 Universtiy of Otago School of Medicine
* To whom correspondence should be addressed. E-mail: kirk.hamilton{at}otago.ac.nz.
Previously, we demonstrated that genistein stimulated Cl- secretion in the mouse jejunum (Baker and Hamilton, Am. J. Physiol. Cell Physiol. 287:C1636-C1645, 2004); however, the mode of action of genistein still remains unclear. Here, we examined the activation of Cl- secretion by the modulation of phosphodiesterases (PDEs) by genistein (75 µM) in the mouse jejunum with the Ussing short circuit current (Isc) technique. Drugs tested included theophylline (10 mM) a non-specific PDE inhibitor; 8-MM-IBMX (100 µM), EHNA (40 µM), milrinone (100 µM) and rolipram (40 and 100 µM), which are specific inhibitors of PDE1 - PDE4, respectively. Theophylline stimulated a bumetanide sensitive Isc, indicative of Cl- secretion, and abolished genistein's stimulatory action on Isc. Neither 8-MM-IBMX nor EHNA altered the basal Isc nor did these PDE inhibitors affect the stimulatory action of genistein on the Isc of the mouse jejunum. Rolipram had no effect on Isc, but reduced the genistein-stimulated Isc compared with time-matched control tissues. Milrinone stimulated a concentration-dependent increase in Isc. Bumetanide (10 µM) inhibited 60 ± 4% of milrinone induced Isc. Pretreating tissues with milrinone prevented genistein from stimulating Isc, and, pre-treatment with genistein reduced the effect of milrinone on Isc. H89 (50 µM), a PKA inhibitor, reduced the milrinone stimulated Isc. Likewise, H89 reduced the bumetanide-sensitive genistein-stimulated Isc. Here, we demonstrate, for the first time, that genistein activates Cl- secretion of the mouse jejunum via inhibition of a PDE3 dependent pathway.
