Novel mechanism for regulation of endothelin synthesis: role of extracellular pH.

ABSTRACT

BACKGROUND/AIMS: Several studies suggest that pH may be an important regulator of renal collecting duct endothelin-1 (ET-1) synthesis; the current study was undertaken to examine this interaction. METHODS: Rat inner medullary collecting duct (IMCD) cells were exposed to varying extracellular pH and ET-1 biosynthetic pathways assessed. RESULTS: Exposure of IMCD to varying pH revealed a strong direct correlation between media pH and both mature ET-1 and Big ET-1 release. A direct correlation also existed between cellular Big ET-1 content and pH. Varying media pH did not alter ET-1 mRNA content nor did it affect activity of a transfected 3.2 kb ET-1 promoter. Media pH did not affect ET-1 degradation nor did it alter IMCD cell total protein synthesis ((3)H-leucine incorporation). Attempts to measure ET-1 mRNA translation rate using His-Tag labeled ET-1 cDNA were not successful. CONCLUSION: pH regulates IMCD ET-1 production through regulation of either mRNA translation or preproET-1 cleavage. This represents a novel mechanism for regulation of ET-1 synthesis.