Genistein potentiates the ANP effect on a K(+)-conductance in HEK-293 cells.
HEK-293 cells are known to reflect many features of the late distal tubule. Furthermore, they have the ability to release urodilatin, the structural analog to ANP. RT-PCR was performed to test for the expression of natriuretic peptide receptors. While the mRNA for the human ANP receptor (NPR-A, GC-A) could be amplified, the CNP-specific receptor NPR-B (GC-B) and the receptor specific for guanylins, GC-C, could not be detected. In patch clamp experiments the effects of ANP (10 nM) on membrane voltage (V(m)) were monitored and HEK-293 cells depolarized by 2.3 +/- 0.5 mV (n=14). In the presence of the EGF receptor blocker genistein (10 microM) the effect of ANP was increased by 65% to 3.9 +/- 0.8 mV (n=14). After removal of genistein the ANP-mediated depolarization further increased by 147% to 5.7 +/- 1.0 mV (n=14). ANP given repetitively without genistein had no increasing depolarizing effect in HEK-293 cells with time. The ANP effect could be fully blocked by 1 mM Ba(2+) and by 1 microM of the specific PKG inhibitor KT5823 indicating that ANP inhibits a K(+)-conductance via a cGMP-dependent protein kinase. Genistein itself hyperpolarized the membrane voltage of HEK-293 cells by -3.9 +/- 0.6 mV (n=11) and this effect could also be fully blocked by Ba(2+) (-0.3 +/- 0.1 mV, n=5), indicating that genistein activates a K(+)-conductance which contributes significantly to the membrane potential of HEK-293 cells.
Hirsch
Jochen
J
Medizinische Klinik und Poliklinik D, Experimentelle Nephrologie, Münster.
Schlatter
Eberhard
E
D009320:Atrial Natriuretic Factor / Q000494:pharmacology*; D001483:Base Sequence; D002460:Cell Line; D017869:Cyclic GMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D017931:DNA Primers; D019833:Genistein / Q000494:pharmacology*; D006162:Guanylate Cyclase / Q000235:genetics; D006801:Humans; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism*; D015221:Potassium Channels / Q000187:drug effects*; D017461:Receptors, Atrial Natriuretic Factor / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000099242:Atrial Natriuretic Factor Receptor B
D009320:Atrial Natriuretic Factor; D017869:Cyclic GMP-Dependent Protein Kinases; D017931:DNA Primers; D019833:Genistein; D006162:Guanylate Cyclase; D011188:Potassium; D015221:Potassium Channels; D017461:Receptors, Atrial Natriuretic Factor; D000099242:Atrial Natriuretic Factor Receptor B; C091715:atrial natriuretic factor receptor A