Comparative quantification of endothelin receptor mRNA in human kidney: new tools for direct investigation of human...

By virtue of its exquisite sensitivity to the effects of endothelin-1 (ET-1), the kidney has been a consistent candidate for a pathophysiologic role for the endothelins. However, observed species differences in both receptor distribution and the subtypes mediating vasoconstriction have necessitated the development of a novel quantitative RT-PCR assay suitable for the direct investigation of human tissue, which is usually available only in very small amounts (i.e., biopsy specimens). In this study we quantified ETA and ETB receptor mRNA in normal renal cortex and medulla. For seven samples, cortex contained 0.19 +/- 0.10 amol ETA mRNA and 1.09 +/- 0.38 amol ETB mRNA/microgram total RNA (mean +/- SEM). In medulla these values were 0.47 +/- 0.25 and 2.17 +/- 1.90, respectively. The ratios of ETA to ETB were about 20:80, which correlates closely with previous studies of expressed receptor protein. This fluorescent nested quantitative RT-PCR assay provides a tool for further investigation of the human ET system at the molecular level in tissue from living individuals, and is of general applicability to the study of endogenous ligand-receptor systems.