Plasma free fatty acid and blood glucose responses to analogues of norepinephrine in man

Abstract

l-Norepinephrine, l-epinephrine, dl-isoproterenol, and l-α-methyl norepinephrine produced pronounced elevations of plasma free fatty acid (FFA) concentrations in five normal subjects during 30-minute constant infusions at dose rates adjusted to give a pressor response of 45 ± 20 mm Hg. dl-Synephrine produced moderate increases, and tyramine produced minimal increases in FFA levels. Equipressor infusions of dopamine, l-phenylephrine, dl-normetanephrine and l-N-methyl epinephrine produced no significant FFA elevations. The observations suggest that, in derivatives of phenylethylamine, hydroxyl substitution at the para position and on the β-carbon and the presence of a primary or secondary amine structure are associated with the potent ability to elicit elevations of FFA in man. The phenolic hydroxyl group in the meta position appears to be of lesser, though significant, importance. Changes in blood glucose concentration did not always correlate with plasma FFA changes. During infusions of dl-isoproterenol, FFA rose significantly while glucose did not. During infusions of dopamine and l-N-methyl epinephrine, glucose rose significantly while FFA did not.