HEAT (hydrochloride)

HEAT (BE2254) hydrochloride is a selective _{alpha 1 adrenergic receptor} antagonist. HEAT hydrochloride, a phenethylamine derivative, shows pK_is of 9, 9.1, and 8.57 for alpha 1a, alpha 1b and alpha 1c, respectively^[1][2]. In Vitro: BE2254 inhibits (-)-noradrenaline-mediated increases in gluconeogenesis with K,sub>B of 0.74 nM^[2].
The alpha-1 selective antagonist [¹²⁵I]BE2254 is used to specifically label a single class of binding sites with a dissociation constant of 131.0 pM and a maximal binding capacity of 17.6 fmol/mg of protein. Catecholamines compete for [¹²⁵I]BE2254 binding stereospecifically and with the characteristic alpha adrenergic potency series of (-)-epinephrine greater than (-)-norepinephrine much greater than (-)-isoproterenol. The alpha-1 selective antagonist prazosin (K_d=2.4 nM) is much more potent in competing for [¹²⁵I]BE2254 binding than is the alpha-2 selective antagonist yohimbine (K_d=2900 nM)^[3].