Phenytoin induces cyclic-AMP accumulation and free fatty acids release in rat brown adipose tissue

The effects of lypolytic processes in rat brown adipose tissue of tetrodotoxin, amiloride, phenytoin, tetraethylammonium and verapamil, drugs affecting Na+, K+ or Ca2+ transmembrane fluxes, were studied with the aim of exploring further the role of these cations in coupling stimulation to lipolysis in this tissue. Phenytoin increased cAMP levels and free fatty acids release in basal conditions and in the presence of isoprenaline. These effects were reversed by substitution of Na+ or K+ by choline or by the addition of ouabain but not of timolol. The other agents studied did not affect lipolysis in basal conditions and in the presence of isoprenaline. The dependence of lipolysis in brown adipose tissue on specific ion channels seems to be excluded in view of these data. However, the possibility of an involvement of brown adipose tissue in the in vivo modification of lipid metabolism induced by phenytoin is suggested.