Long-term blood pressure telemetry in AT2 receptor-disrupted mice.
OBJECTIVE
The hypertension in AT2 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 AT2 receptor knockout and wild-type mice to measure blood pressure, heart rate, aortic pressure dp/dt, 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 AT2 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 AT2 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 AT2 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.


CONCLUSIONS
These data suggest that AT2 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.
Gross
V
V
Franz Volhard Clinic and Max Delbrück Center for Molecular Medicine, Medical Faculty of the Charité, Humboldt University of Berlin, Germany.
Milia
A F
AF
Plehm
R
R
Inagami
T
T
Luft
F C
FC
D000818:Animals; D001794:Blood Pressure / Q000502:physiology*; D001795:Blood Pressure Determination / Q000379:methods*; D002940:Circadian Rhythm / Q000502:physiology*; D003900:Desoxycorticosterone / Q000633:toxicity; D005500:Follow-Up Studies; D006339:Heart Rate / Q000502:physiology; D006973:Hypertension / Q000139:chemically induced / Q000503:physiopathology*; D008124:Locomotion / Q000502:physiology; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D044140:Receptor, Angiotensin, Type 1; D044139:Receptor, Angiotensin, Type 2; D011945:Receptors, Angiotensin / Q000097:blood*; D012982:Sodium, Dietary / Q000633:toxicity; D013686:Telemetry
D044140:Receptor, Angiotensin, Type 1; D044139:Receptor, Angiotensin, Type 2; D011945:Receptors, Angiotensin; D012982:Sodium, Dietary; D003900:Desoxycorticosterone