Role of prostaglandin I2 and thromboxane A2 in the regulation of blood pressure

Abstract

To clarify the role of prostacyclin (PG) I2 and thromboxane (TX) A2 in the regulation of blood pressure from the standpoint of acquired factors and hereditary factors, the following experiments were carried out. [1] A low salt diet (2 g/day) was given for 7 days, followed by a high salt diet (23 g/day) for 7 days to 34 patients with essential hypertension. The percent change in 6-keto-PGF1 alpha by salt loading was directly proportional to that in mean blood pressure, but there was no significant relationship between the percent change in TXB2 and that in mean blood pressure. [2] The aorta was removed from 5-week-old and 20- to 25-week-old spontaneously hypertensive rats (SHRs) and age-matched Wistar Kyoto (WKY) rats. Each aorta was incubated in Tris buffer with and without arachidonic acid (AA). There was no significant difference in 6-keto-PGF1 alpha production between SHRs and WKY rats at the age of 5 weeks, but the aorta obtained from 20- to 25-week-old SHRs synthesized about 1.5 times as much 6-keto-PGF1 alpha as did that from age-matched WKY rats with and without AA. The aorta from 5-week-old SHRs synthesized more TXB2 than did that from age-matched WKY rats with and without AA, but there was no significant difference in TXB2 production between SHRs and WKY rats at the age of 20-25 weeks. These data suggest that the plasma PGI2 may have increased as a homeostatic reaction to the elevation of blood pressure induced by salt loading.(ABSTRACT TRUNCATED AT 250 WORDS)