Natriuretic peptide receptor-A is functionally expressed on bullfrog retinal Müller cells.
By the patch clamp technique, whole-cell currents induced by brain natriuretic peptide (BNP) from isolated bullfrog retinal Müller cells were studied. Application of 100 nM BNP induced a sustained inward current from these cells with a reversal potential of about 0 mV, and the current could be completely blocked by anantin, an antagonist of the A-type NP receptor (NPR-A) and CdCl(2), a blocker of cyclic nucleotide-gated (CNG) non-selective cation channels. Likewise, perfusion with the membrane-permeable cGMP analog 8-bromoguanosine-3',5'-cyclic monophosphate (8Br-cGMP) caused effects that are similar to those of BNP. Moreover, application of BNP failed to induce any current in the presence of 1 mM 8Br-cGMP. By calcium imaging, we further showed a significant increase in intracellular calcium levels ([Ca(2+)](i)) of all parts of Müller cells, including the endfoot, soma and processes following the perfusion of BNP, and the increase could be blocked by anantin. All these results suggest that NPR-A is expressed in bullfrog Müller cells, and activation of the receptor causes an increase of intracellular cGMP levels that activates CNG channels and thereby results in an increased calcium influx.
Cao
Li-Hui
LH
Institute of Neurobiology, Institutes of Brain Science, Fudan University, 138 Yixueyuan Road, Shanghai 20032, PR China.
Yang
Xiong-Li
XL
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002469:Cell Separation; D000242:Cyclic AMP / Q000378:metabolism; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000494:pharmacology; D003952:Diagnostic Imaging; D005456:Fluorescent Dyes; D016257:Fura-2; D007091:Image Processing, Computer-Assisted; D066298:In Vitro Techniques; D020097:Natriuretic Peptide, Brain / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D010456:Peptides, Cyclic / Q000494:pharmacology; D011892:Rana catesbeiana; D017461:Receptors, Atrial Natriuretic Factor / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D012160:Retina / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*
D005456:Fluorescent Dyes; D010456:Peptides, Cyclic; C058930:brain natriuretic peptide receptor; D020097:Natriuretic Peptide, Brain; C068090:anantin; C016276:8-bromocyclic GMP; D000242:Cyclic AMP; D017461:Receptors, Atrial Natriuretic Factor; D006152:Cyclic GMP; D002118:Calcium; D016257:Fura-2