Different effects of aspirin on blood pressure of spontaneously hypertensive rats (SHR) with high and spontaneously low levels of blood pressure.

Spontaneously hypertensive rats (SHR) of the Okamoto strain with blood pressure above 161 mmHg and SHR with blood pressure levels of less than 160 mmHg were treated with oral doses of aspirin (100 mg kg-1) for three days. Whereas the blood pressure of SHR with blood pressure above 161 mmHg was decreased by aspirin, the blood pressure of SHR below 160 mmHg was increased by aspirin. The extent and direction of blood pressure change by aspirin was strongly correlated with the blood pressure of SHR before treatment (r = -0.88). The effect of aspirin supports an important role for endogenous prostanoids in the regulation of blood pressure of SHR.