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The possible role of arachidonic acid metabolites in the regulation of arterial blood pressure was investigated in rats receiving 0, 5, or 9 energy (en) % linoleic acid in their diet (groups 1-3) over 6 wk. In group 1 animals, systolic arterial blood pressure significantly increased from 100.5 +/- 2.0 to 110.6 +/- 3.1 mmHg (P less than 0.01) after 6 wk of dietary linoleic acid deprivation, whereas no effect on blood pressure was observed in group 2 and 3 animals receiving dietary linoleic acid supplements. Generation of prostacyclin (PGI2)-like activity by isolated aorta from rats fed the different diets was determined using a platelet-aggregation bioassay following incubation of aortic tissue for 12, 15, and 30 min, respectively. In isolated aorta from rats fed the 5 en% linoleic acid, production of PGI2 was 55.9 +/- 1.2, 70.5 +/- 2.6, and 90.9 +/- 3.6 pmol/mg over the three incubation periods. In group 1 animals, a significant suppression of PGI2 generation to 35.4 +/- 1.5, 41.1 +/- 1.7, and 55.0 +/- 1.2 pmol/mg (P less than 0.005) was observed, whereas PGI2 production was unaltered in aortic tissue from group 3 animals. In contrast, plasma concentrations of circulating thromboxane B2 were highest in group 1 animals (2.15 +/- 0.38 pmol/ml) and measured 1.28 +/- 0.17 and 0.83 +/- 0.10 pmol/ml in group 2 and 3 animals, respectively. Our results demonstrate that dietary deprivation of the arachidonic acid precursor linoleic acid increases arterial blood pressure that is associated with a suppression of vascular PGI2 synthesis and, most likely, a secondary rise in circulating thromboxane concentrations.

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The present study investigates whether the synthesis of prostacyclin (PGI2) in isolated rat aorta is dependent on the state of sodium balance of the animals. Three groups of ten rats each were included into the study. Two of them were fed a diet low in NaCl for 10 days with group I receiving 0.9% saline and group II distilled water as drinking fluid. Group III received a regular rat chow containing approximately 0.8 mmol day-1 of sodium, also for 10 days. At the end of the dietary protocol, systolic arterial blood pressure was significantly higher in group I (109.9 +/- 2.4 mmHg) as compared to group II (101.0 +/- 2.4 mm Hg; P less than 0.05) and group III animals (102.2 +/- 1.6 mm Hg; P less than 0.05). Generation of PGI2-like activity was determined in portions of the animals' isolated aorta using a platelet aggregation bioassay following incubation in 0.05 M Tris buffer (pH 9.3) for 12, 15, and 30 min, respectively. During these incubation times, generation of PGI2-like activity averaged 48.6 +/- 3.5, 57.8 +/- 4.3 and 68.3 +/- 3.2 pmol mg-1 in group III animals, which had received the regular rat chow, with similar values in the low salt group II (50.2 +/- 2.5, 57.7 +/- 2.7 and 72.9 +/- 3.7 pmol mg-1). Aortic generation of PGI2-like material was significantly suppressed in the high salt group I (37.5 +/- 2.8, 46.2 +/- 3.2 and 61.3 +/- 4.0 pmol mg-1; P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)