New insights on the functions of the guanylyl cyclase receptors.

The discovery of at least 29 genes encoding putative guanylyl cyclases in Caenorhabditis elegans has raised the question as to whether there are numerous receptors yet to be discovered in the mammal. The nematode, however, not only seems ideal to study guanylyl cyclase receptor localization and function, given the large variety of isoforms, but also leads to possible identification of ligands for orphan guanylyl cyclases by the use of genetic and behavioral assays. A recent powerful approach to describe the function of different guanylyl cyclase isoforms in mammals has been the disruption of the corresponding genes in the mouse. A salt resistant elevation of blood pressure, which corresponds to the phenotype of 50% of all human patients with essential hypertension, is observed in mice lacking the GC-A-receptor. Mice missing the GC-C receptor have been shown to be resistant to STa, an E. coli heat-stable enterotoxin, which is largely responsible for travellers diarrhea in adults and mortality due to diarrhea in infants.