Effect of prostaglandins on bradykinin-induced visceral-cardiac reflexes

We examined the effect of prostaglandins on the reflex cardiovascular response to bradykinin applied to the abdominal organs of anesthetized cats. Bradykinin (10 μg/ml) was applied to the serosal surface of the stomach, gallbladder, or jejunum before and after injection of indomethacin (2-10 μg/ml iv) and after application of 1 μg/ml of prostaglandins E₁, E₂, or F(2α) (PGE₁, PGE₂, PGF(2α)) or prostacyclin (PGI₂). In six cats, stimulation of the stomach with bradykinin significantly increased mean arterial pressure (MAP) by 37 ± 5 (SE) mmHg and maximal dP/dt by 633 ± 101 mmHg/s. Following indomethacin the bradykinin-induced increased in MAP and dP/dt were significantly reduced to 19 ± 4 mmHg and 191 ± 58 mmHg/s, respectively. Treatment with PGE₁, PGE₂, or PGI₂, but not PGF(2α), restored the initial bradykinin response. The gallbladder and jejunum responded similarly. Also application of exogenous prostaglandins, PGE₂ or PGI₂, to the stomach, gallbladder, or jejunum significantly augmented the cardiovascular response to bradykinin. Finally, PGE₂ restored a portion of the cardiovascular response to bradykinin following the development of tachyphylaxis. We conclude that prostaglandins are necessary for the full manifestation of the cardiovascular response to bradykinin.