Abstract

The effect of histamine on serum free fatty acid (FFA) and glycerol levels was examined in humans and dogs in vivo. By the end of a 15-minute infusion of histamine diphosphate (11 mug of histamine per min i.v.), FFA levels in six male human volunteers had risen from basal values of 424 +/- 41 (mean +/- S.E.M.) to 909 +/- 45 muEq/1, and glycerol levels had risen from 66 +/- 5.5 to 124 +/- 9.3 mumol/1. These effects in man were not blocked by diphenhydramine, an H1-receptor antagonist, but were entirely blocked by propranolol, a beta adrenergic antagonist. Similar infusions of histamine (11 mug/min i.v.) in six anesthetized dogs caused FFA levels to rise from 189 +/- 13 to 461 +/- 92 muEq/1 and glycerol levels to rise from 58 +/- 3.7 to 157 +/- 22.4 mumol/1. These effects in the dog were not blocked by diphenhydramine or by propranolol but were entirely blocked by metiamide, an H2-receptor antagonist. These observations illustrate that low levels of histamine in vivo can produce significant elevations of serum FFA and glycerol levels in both humans and dogs. These results further suggest that the action of histamine in humans is indirect whereas the effect in dogs may be due to a direct action of histamine at the H2-receptor in canine adipose tissue.