We investigated whether or not Relaxin ameliorates the hypertension induced damage to heart and kidney. We used double transgenic rats harboring both human renin and angiotensinogen genes (dTGRs). These rats develop moderately severe Hypertension but die of end-organ cardiac and renal damage by week 7. Untreated dTGRs had an around 50% mortality rate at 7 weeks. The heart shows necrosis and fibrosis, whereas the kidneys esemble the hemolytic-uremic syndrome vasculopathy.
We started Relaxin-treatment on four weeks old dTGR in low (26 μg/kg/d) and high dose (240 μg/kg/d) and age-matched SD rats. Blood-pressure- and albuminuria-measurements were monitored during the treatment period (three weeks). Seven weeks old animals were killed, hearts and kidneys were isolated and used for histochemical and quantitative TaqMan RT-PCR analysis. Systolic blood pressure increased progressively in untreated dTGRs from 161.6 ± 3.02 mmHg in week 5 to 225.3 ± 4.48 mmHg in week 7. Relaxin treatment had no significant influence on blood pressure (low dose 208.0 ± 5.51 mmHg and high dose 222.2 ± 5.60 mmHg at week 7 ) whereas SD rats were normotensive (106.3 ± 1.15 mmHg). Untreated (5.38 ± 0.13 mg/g) and Relaxin treated dTGRs (low dose 5.20 ± 0.18 mg/g and high dose 5.33 ± 0.29 mg/g) had similar cardiac hypertrophy indices (heart-to-body weight ratio), which were significantly higher compared with nontransgenic SD rats (2.90 ± 0.08 mg/g). BNP and CTFG mRNA expression in the hearts was significant higher in untreated dTGRs compared to SD rats. There were no differences in BNP and CTFG expression between untreated and Relaxin treated dTGRs. Relaxin treatment (low dose 78502 ± 16848 μg/day and high dose 43642 ± 10852
μg/day at week 7) did not ameliorate albuminuria compared with untreated dTGRs (57937 ± 6122 μg/day at week 7). Furthermore the treatment with Relaxin did not prevent matrix deposition in the heart and kidney of d TGRs. Finally, Relaxin treatment did not reduce mortality. Although survival was 52 %, in untreated dTGRs 36 % in low dose and 54 % high dose Relaxin treated dTGRs at week 7.
These data demonstrate that Relaxin did not improve angiotensin II-induced target organ damage.