Studies with guanosine-5'-monophosphate (GMP): new method for measurement and effects on blood pressure.

A practical new method for measuring serum guanosine-5'-monophosphate (GMP) was developed and three experiments were performed using this method. In the first, we observed the reduction of blood pressure (BP) and the elevation of serum GMP level persisting for 3 hours in male Japanese White Rabbits administered GMP, 50 mg/kg given as a single oral dose. In the second, 6-week-old male spontaneously hypertensive rats (SHR) received GMP, 200 mg/kg/day, orally for 8 weeks. The systolic BP in the GMP-treated rats, which averaged 170.2 mmHg, was lower than that of the control group, which averaged 188.0 mmHg. Arteriosclerotic findings were milder in the GMP-treated SHR as compared to the control. In the third experiment, the serum GMP level was measured in humans. We observed a significant negative correlation between the serum GMP concentration and systolic or diastolic BP. In conclusion, GMP reduced the BP in experimental animals, suggesting that it may be useful as an antihypertensive agent.