[(3)H]Nicotine binding in peripheral blood cells of smokers is correlated with the number of cigarettes smoked per day.

The principal sites for biological action of tobacco products are thought to be the nicotinic acetylcholine receptors (nAChR). Nicotinic receptor subunit genes, therefore, represent an important gene family for study in nicotine addiction. They are localized in both brain and in the periphery. In brain these receptors appear to function as modulators of synaptic transmission; the function of peripheral receptors is not known. Nicotinic receptor levels in human brain are regulated by smoking in a dose-dependent manner. In peripheral blood, nicotinic receptors are present on both lymphocytes and polymorphonuclear cells (PMN). We have compared [(3)H]nicotine binding in PMN isolated from smokers and non-smokers. [(3)H]nicotine binding was increased in smokers and was correlated, as in brain, with tobacco use. Expression of both mRNA and protein in lymphocytes and PMN, for a subset of nicotinic receptor subunits, suggests that these cell types contain both alpha4beta2 and alpha3beta4 receptors.