STIMULATION BY ANGIOTENSIN OF PROSTACYCLIN BIOSYNTHESIS IN RATS AND DOGS

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Abstract
SUMMARY: 1. Stimulation of prostanoid release by angiotensins (AI and All) in rat isolated mesenteric vasculature and in the circulation of anaesthetized dogs has been investigated by bioassay.2. AI and All released a PGI2‐like substance into rat mesenteric effluent and arterial blood of dogs; PGE2, PGF2α or TXA2 were not detected.3. AI stimulated PGL release in both systems largely as a result of its conversion to All, since PGI2 release was much reduced after treatment with captopril.4. Intravenous AII (0‐2‐1.0μg kg−1min−1) in dogs released PGI2 mainly from the lungs since right atrial blood contained much less than arterial blood.5. Indomethacin (1 μg/ml) abolished All‐induced PGI2 release from the mesentery preparation, but intravenous indomethacin (10 mg/kg), meclofena‐mate (2 mg/kg) or aspirin (100 mg/kg) did not eliminate the pulmonary source of PGI2 in dogs. These findings highlight the dangers of assuming in vivo treatment with cyclo‐oxygenase inhibitors abolishes biosynthesis of all prostanoids.