Long-term blood pressure telemetry in AT2 receptor-disrupted mice

Objectives The hypertension in AT(2) receptor knockout mice is imperfectly defined. Therefore, we investigated the influence of dietary salt loading and deoxycorticosterone (DOCA)-salt treatment on blood pressure and diurnal patterns of blood pressure in these mice by radiotelemetry, Methods We used telemetry in AT(2) receptor knockout and wild-type mice to measure blood pressure, heart rate, aortic pressure d p/d t, locomotor activity, and circadian rhythms, Salt-related effects were studied by increasing the salt in chow to 4%, adding 1% saline in drinking water, and by DOCA-salt treatment, Results Baseline blood pressures were higher in AT(2) receptor knockout than in wild-type mice and were not affected by increasing the salt intake, The blood pressure increase was steeper and greater in AT(2) receptor knockout than in wild-type mice after DOCA-salt treatment, A circadian rhythm of blood pressure and heart rate, with higher values during the night, was seen in wild-type, but not in AT2 receptor knockout mice. In AT(2) receptor knockout mice, this rhythm was only significant when daily salt intake was increased or when DOCA-salt hypertension was induced. The acrophase of blood pressure and heart rate was found between 2000 and 2400 h and was in accordance with the maximum physical activity. Conclusion These data suggest that AT(2) knockout mice display slight hypertension which is not salt-sensitive, On the other hand, the susceptibility to develop DOCA-salt hypertension is increased. The study also illustrates the power of telemetry in monitoring long-term cardiovascular changes and circadian blood pressure and heart rate rhythms in genetically engineered mice. J Hypertens 2000, 18:955-961 (C) Lippincott Williams & Wilkins.