type 6.6 kB SacI genomic fragment or the disrupted 8.4 kB SacI genomic fragment. The presence of the Butein site tie-esACE transgene is indicated by hybridization of the probe with a 3.7 kB fragment. Materials and Methods Generation of target vector We used Wt rabbit sACE cDNA to generate esACE, by deletion of the transmembrane and cytoplasmic domain coding region. The esACE cDNA was then used to generate Tie-esACE construct, as described previously. The expression and secretion of ACE was tested by transient transfection of the tieesACE plasmid in human fibrosarcoma cells followed by Western Blotting of the cell extracts and culture medium. The Tie-esACE-BGHpA transgene was subsequently released from this plasmid by SpeI and AsnI digestion and sent to the University of Cincinnati Transgenic Mouse Core Facility for the generation of transgenic mice utilizing standard techniques. ACE enzyme activity assay The enzymatic activity of ACE was assayed using Hip-His-Leu as a substrate and measuring fluorimetrically the His-Leu liberated at 5 mM of Hip-His-Leu. Serum from retro-orbital eye bleed or tissue homogenates of the transgenic mice were used to measure ACE enzymatic activity. Activity values are reported as mmoles His-Leu per per ml of serum or 25 mg of tissue protein extract liberated from Hip-His-Leu after one-hour incubation at 37uC. Establishment of transgenic mice The tie-esACE transgene was microinjected into the pronuclei of FVB strain zygotes using standard techniques. Adult FVB tieesACE-BGHpA transgenic founder mice were mated with Ace+/2 FVB mice to generate Ace+/2 TeS+/2 mice. Interbreeding between male and female Ace+/2, TeS+/2 mice within the same line was performed to generate the Ace-/-, TeS/TeS. Genotyping of all mice was performed by Southern Blotting as described below. Expression of esACE in the transgenic line was confirmed by Western Blotting of the serum using anti-ACE antibody. All of the mice described in this study, including Wt, KO, Tie-esACE and Tie-sACE, were of the FVB strain. All mouse experimental protocols were Plasma renin activity Blood was collected by retro-orbital sinus plexus eye bleed under brief isoflurane anesthesia and plasma renin activity was measured as described before. Briefly, plasma renin activity, defined as the rate of Ang I generation from renin in the sample and excess exogenous substrate provided from nephrectomized rat plasma, was incubated at pH 6.5 and pH 8.5 for 90 minutes. Ang I generated in the sample was quantified PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/19648918 by radioimmunoassay. Serum creatinine measurement Serum creatinine levels were determined by previously described alkaline picrate method. Standards Strain Wt Transgene None Genotype Ace +/+ ACE isoform Somatic Expression Vascular endothelial cells Proximal tubule cells Brain Leydig cells Germinal KO Ts TeS None Tie-sACE Tie-esACE Ace -/Ace -/-Ts/Ts Ace -/- TeS/TeS None Somatic Somatic Sperm None Vascular endothelial cells Vascular endothelial cells doi:10.1371/journal.pone.0087484.t001 
2 Secreted ACE Cannot Restore Normal Blood Pressure or 20 ml of serum were added into a 96-well microtiter plate. Alkaline picrate solution was added and incubated for 10 min at RT, absorbance was read at 490 nm. After the absorbance measurement, 60% acetic acid was added into all wells and left for 8 min at RT. The absorbance was read at 490 nm again, and subtracted from the first absorbance. Angiotensin II measurements For each genotype, blood from four age matched adult mice was pooled to ach
