The renin-anglotensin system (RAS) is the most important regulatory system of electrolyte homeostasis and blood pressure. We report here the development of transgenic rats carrying the human angiotensinogen TGR-(hAOGEN) and human renin TGR(hREN) genes. The plasma levels and tissue distribution of the transcription and translation products from both genes are described. A unique species specificity of the enzyme kinetics was observed. The human RAS components in the transgenic rats did not interact with the endogenous rat RAS in vivo. Insead, infusions of exogenous human RAS components specifically interacted with human transgene translation products. Thus, iion of human renin in TGR(hAOGEN) led to an increase of angioensin H and an elevation of blood pressure, which could not be antagonized by the human-specific renin enzyme inhibitor Ro 42-5892. Rat renin also elevated blood pressure and angiotensin H in TGR(hAOGEN); however, this effect was not antagonized by the human renin inhibitor. Compared to mice, rats offer the advantage of chronic instrumentation and repetitive, sophisticated, hemodynamic, and endocrinological investigations. Thus, transgenic rat models with human-specific enzyme kinetics permit primate-specific analyses in non-primate in vivo and in vitro experimental systems.The successful incorporation of renin-angiotensin (RAS) genes into transgenic mice has been reported (1, 2). Rats, on the other hand, present specific technical problems with respect to the generation of transgenic animals. The transgenic rats TGR(mREN2)27, which harbor a mouse renin gene and exhibit fulminant hypertension, provided evidence for a monogenetic form of hypertension (3).Transgenic mice harboring the genes of mouse renin and angiotensinogen (2), rat renin and angiotensinogen (4), as well as human renin (1) have been described. Thus far, most ofthe RAS gene constructs used for the generation of transgenic animals interacted directly with the host RAS (2, 4).Since the genetic background for the transgenes appears to be of primary importance for the development of hypertension (5), we developed transgenic rats harboring the complete human renin TGR(hREN) and human angiotensinogen TGR(hAOGEN) genes. These rats allow studies into the regulation of human genes in non-primate animal models (6). In vitro, the species specificity of human renin and angiotensinogen is well known. Transgenic animals permit the study of specific interactions with the human transgene products in vivo, without interference from the host RAS.EXPERIMENTAL PROCEDURES Transgenic Techniques. Linear DNA fiagments consisting of either the entire human renin gene (1, 7) or the entire human angiotensinogen gene (8), as described elsewhere (1, 3), were injected into the male pronuclei offertilized, outbred Sprague-Dawley (SD) rat eggs.Immnnalyses of Renin and en. Human renin was immunologically measured in transgenic rat plasma. The direct and specific measurement of human renin used two pairs of monoclonal antibodies in an immunoradiometric assay. ...

Purpose Relaxation‐compensated CEST‐MRI (i.e., the inverse metrics magnetization transfer ratio and apparent exchange‐dependent relaxation) has already been shown to provide valuable information for brain tumor diagnosis at ultrahigh magnetic field strengths. This study aims at translating the established acquisition protocol at 7 T to a clinically relevant magnetic field strength of 3 T. Methods Protein model solutions were analyzed at multiple magnetic field strengths to assess the spectral widths of the amide proton transfer and relayed nuclear Overhauser effect (rNOE) signals at 3 T. This prior knowledge of the spectral range of CEST signals enabled a reliable and stable Lorentzian‐fitting also at 3 T where distinct peaks are no longer resolved in the Z‐spectrum. In comparison to the established acquisition protocol at 7 T, also the image readout was extended to three dimensions. Results The observed spectral range of CEST signals at 3 T was approximately ±15 ppm. Final relaxation‐compensated amide proton transfer and relayed nuclear Overhauser effect contrasts were in line with previous results at 7 T. Examination of a patient with glioblastoma demonstrated the applicability of this acquisition protocol in a clinical setting. Conclusion The presented acquisition protocol allows relaxation‐compensated CEST‐MRI at 3 T with a 3D coverage of the human brain. Translation to a clinically relevant magnetic field strength of 3 T opens the door to trials with a large number of participants, thus enabling a comprehensive assessment of the clinical relevance of relaxation compensation in CEST‐MRI.

Transgenic mice were generated by injecting the entire rat angiotensinogen gene into the germline of NMRI mice. The resulting transgenic animals were characterized with respect to hemodynamics, parameters of the renin angiotension system, and expression of the transgene. The transgenic line TGM(rAOGEN)123 developed hypertension with a mean arterial blood pressure of 158 mmHg in males and 132 mmHg in females. In contrast, the transgenic line TGM(rAOGEN)92 was not hypertensive. Rat angiotensinogen was detectable only in plasma of animals of line 123. Total plasma angiotensinogen and plasma angiotensin II concentrations were about three times as high as those of negative control mice. In TGM(rAOGEN)123 the transgene was highly expressed in liver and brain. Transcripts were also detected in heart, kidney and testis. In TGM(rAOGEN)92 the brain was the main expressing organ. In situ hybridization revealed an mRNA distribution in the brain of TGM(rAOGEN)123 similar to the one in rat. In TGM(rAOGEN)92 the expression pattern in the brain was aberrant. These data indicate that overexpression of the angiotensinogen gene in liver and brain leads to the development of hypertension in transgenic mice. The TGM(rAOGEN)123 constitutes a high angiotensin II type of hypertension and may provide a new experimental animal model to study the kinetics and function of the renin angiotensin system.