Role of bradykinin in postprandial hypotension in humans

A transient significant decrease in mean arterial blood pressure (MAP) from 107 +/- 3 to 98 +/- 3 mmHg (P<0.05) was observed in elderly (59-69 years o f age), healthy volunteers 25-30 min following ingestion of a test meal. In young volunteers (22-34 years of age), a postprandial decrease of MAP from 88 +/- 3 to 83 +/- 4 mmHg was also noted but it was not statistically sign ificant. A 40% decrease in bradykinin (BK) content of circulatory high mole cular weight kininogen had previously been observed in human subjects given the same test meal. We presently demonstrate by specific ELISA that the st able pentapeptide metabolite (1-5 BK) of BK increases from 2.5 +/- 1.0 to 1 1.0 +/- 2.5 pg/ mi plasma (P<0.05) in elderly volunteers and from 2.0 +/- 1 .0 to 10.3 +/- 3.2 pg/ml plasma (P<0.05) in young volunteers 3 h following food intake. This result suggests that ingestion of food stimulates BK rele ase from kininogen in normal man. Postprandial splanchnic vasodilatation, d emonstrated by a decrease of plasma half-life of intravenously administered indocyanine green (ICG), a marker of mesenteric blood flow to the liver, f rom 4.4 +/- 0.4 to 3.0 +/- 0.1 min (P<0.05) in young volunteers and from 5. 2 +/- 1.0 to 4.0 +/- 0.5 min (P<0.05) in elderly volunteers, accompanied BK release. The participation of BK in this response was investigated in subj ects given the BK-potentiating drug captopril prior to food intake. Postpra ndial decreases of ICG half-lives were not changed by this treatment in eit her young or elderly subjects, a result which may indicate that BK released following food intake plays no role in postprandial splanchnic vasodilatat ion in normal man.