TY - JOUR T1 - THE PRESENCE OF ANTAGONISTICALLY ACTING <em>ALPHA</em> AND <em>BETA</em> ADRENERGIC RECEPTORS IN THE MOUSE SPLEEN JF - Journal of Pharmacology and Experimental Therapeutics JO - J Pharmacol Exp Ther SP - 72 LP - 80 VL - 160 IS - 1 AU - Louis J. Ignarro AU - Elwood Titus Y1 - 1968/03/01 UR - http://jpet.aspetjournals.org/content/160/1/72.abstract N2 - The data presented in this report indicate that both alpha and beta adrenergic receptors exist in the spleen of the mouse. Responses of the isolated whole spleen were measured by a sensitive isotonic transducer. Contractions elicited by l-norepinephrine (l-NE), l-epinephrine (l-E) and dl-isoproterenol (dl-ISO) were antagonized reversibly by phentolamine and irreversibly by phenoxybenzamine. Low and high concentrations of dl-ISO produced relaxation and contraction, respectively, of splenic smooth muscle. The relaxation elicited by dl-ISO was reversibly antagonized by propranolol and MJ 1999 (4-(2-isopropylamino-1-hydroxyethyl)methanesulfonanilide hydrochloride). In the presence of phenoxybenzamine, an alpha receptor antagonist, only relaxation was elicited by l-E and dl-ISO. Intrinsic activities (alpha) and affinities (pD2) of l-NE, l-E and dl-ISO for alpha receptors were determined. Activities for alpha receptors fell in the order dl-ISO l-NE ≤ l-E. Affinities for alpha receptors increased in the order, dl-ISO l-E l-NE. The relative order of increasing intrinsic activities for beta receptors was the reverse of that for alpha receptors, l-NE l-E dl-ISO. The affinities of reversible and irreversible antagonists, pA2 and pD'2 values, respectively, for alpha receptors were also determined. © 1968 by The Williams &amp; Wilkins Company ER -