G protein-coupled receptor for nicotinic acid in mouse macrophages

The use of the HDL-elevating drug nicotinic acid in the treatment and prevention of atherosclerotic disease is limited by the frequent induction of skin flushing. The therapeutic effects of nicotinic acid are attributed to inhibition of lipolysis in adipose tissue via a G protein-coupled receptor, whereas the mechanism of flush induction by release of prostaglandin D(2) from macrophages is not understood. In this study, we investigated if macrophages contain nicotinic acid receptors. Specific guanine nucleotide sensitive binding sites for [(3)H]nicotinic acid were detected in membranes from mouse RAW 264.7 macrophages. Nicotinic acid and related heterocycles stimulated activation of pertussis toxin-sensitive G proteins. The rank orders of potency in macrophage membranes were identical for inhibition of [(3)H]nicotinic acid binding and G protein activation, and were pharmacologically indistinguishable from that of the G protein-coupled nicotinic acid receptor in spleen membranes. These results indicate that the effects of nicotinic acid on macrophages, spleen and probably adipocytes are mediated via an identical, unique G protein-coupled receptor.