Effect on apparent liver blood flow of histamine-receptor blockers and inhibition of prostaglandin synthesis

Abstract

We have recently shown that histamine H2-receptor blockade with cimetidine reduces apparent liver blood flow. To determine the effects of inhibition of prostaglandin synthesis and of H1-receptor blockade and of their additive effects when combined with cimetidine (600 mg), we estimated liver blood flow from the clearance of a single dose (0.5 mg/kg) of indocyanine green (ICG) in six healthy subjects after indomethacin (50 mg. three times during 24 hr) and chlorpheniramine (8 mg. three times during 24 hr). Indomethacin and chlorpheniramine reduced ICG estimated liver blood flow by 18 +/- 3% and 13 +/- 4% (mean +/- SEM). When cimetidine was added to indomethacin or chlorpheniramine, the reductions in flow of 22 +/- 6% and 19 +/- 5% were not significantly greater than that after indomethacin, chlorpheniramine, or cimetidine alone (16 +/- 6%). These data suggest that both histamine acting through H1- and H2-receptors and prostaglandins may influence liver blood flow in man and are consistent with evidence from animal experiments that suggest a role for prostaglandins in H2-mediated vascular responses.