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Heart failure in humans is characterized by alterations in myocardial adrenergic signal transduction, the most prominent of which is down-regulation of ftl-adrenergic receptors. We tested the hypothesis that down-regulation of fl1-adrenergic receptors in the failing human heart is related to decreased steady-state levels of 61 receptor mRNA. Due to the extremely low abundance of fih receptor mRNA, measurements were possible only by quantitative polymerase chain reaction (QPCR) or by RNase protection methods. Because the j8 receptor gene is intronless and 81 receptor mRNA abundance is low, QPCR yielded genomic amplification in total RNA, and mRNA measurements had to be performed in poly(A)'-enriched RNA. By QPCR the concentration of jI receptor mRNA varied from 0.34 to 7.8 X 107 molecules/,g poly(A)'-enriched RNA, and the assay was sensitive to 16.7 zeptomol. Using 100-mg aliquots of left ventricular myocardium obtained from organ donors (nonfailing ventricles, n = 12) or heart transplant recipients (failing ventricles, n = 13), the respective jI mRNA levels measured by QPCR were 4.2±0.7 X 107/,ug vs. 2.10±0.3 X 107/i.tg (P = 0.006). In these same nonfailing and failing left ventricles the respective jBI-adrenergic receptor densities were 67.9±6.9 fmol/mg vs. 29.6±3.5 fmol/mg (P = 0.0001). Decreased mRNA abundance in the failing ventricles was confirmed by RNase protection assays in total RNA, which also demonstrated a 50% reduction in #1 message abundance. We conclude that down-regulation of 01 receptor mRNA contributes to down-regulation of #I adrenergic receptors in the failing human heart. (J. Clin. Invest. 1993. 92:2737-2745

AT1 receptors are selectively downregulated in failing human ventricles, similar to the selective downregulation of beta 1 receptors. The relative lack of AT1 downregulation in ISC hearts may be related to differences in the degree of ventricular dysfunction.

The gonadotropin releasing hormone (GnRH) gene encodes a protein which plays a critical role in mammalian reproductive physiology. Its expression is predominantly restricted to the hypothalamus although it has also been described in the placenta. To begin to determine the promoter elements important for tissue specific expression and to examine the mechanisms of developmental and hormonal regulation of the rat GnRH (rGnRH) gene, we cloned the rGnRH gene from a rat liver genomic DNA library. The nucleotide sequence of greater than 3 kb of 5'-flanking region was determined. The transcriptional initiation site in rat hypothalamic tissue and a mouse hypothalamic cell line were mapped by primer extension analysis and found to be different. In addition, transient transfection studies demonstrated that multiple regions of the distal promoter are important for tissue specific and basal promoter activity in hypothalamic cells. Furthermore, in these cells a potent activation region resides between -3026 and -1031 bp and suppressor region between -1031 and -903 bp upstream of the transcriptional start site. We conclude that different portions of the 5'-flanking region, which are activating and suppressing in nature, are critical for hypothalamic expression of the rGnRH gene.