Beta-adrenoceptors in human tracheal smooth muscle: characteristics of binding and relaxation

• Published in: Life sciences (1973) Vol. 40; no. 26; p. 2561
• Main Authors: van Koppen, C J, Hermanussen, M W, Verrijp, K N, Rodrigues de Miranda, J F, Beld, A J, Lammers, J W, van Ginneken, C A
• Format: Journal Article
• Language: English
• Published: Netherlands 29.06.1987
• Subjects: Atenolol - metabolism; Binding, Competitive; Humans; In Vitro Techniques; Muscle Contraction; Muscle Relaxation; Muscle, Smooth - metabolism; Pindolol - analogs & derivatives; Pindolol - metabolism; Propranolol - metabolism; Receptors, Adrenergic, beta - metabolism; Receptors, Adrenergic, beta - physiology; Sarcolemma - metabolism; Stereoisomerism; Trachea - metabolism; Trachea - physiology
• ISSN: 0024-3205
• DOI: 10.1016/0024-3205(87)90079-8

Specific binding of [125I]-(-)-cyanopindolol to human tracheal smooth muscle membranes was saturable, stereo-selective and of high affinity (Kd = 5.3 +/- 0.9 pmol/l and RT = 78 +/- 7 fmol/g tissue). The beta 1-selective antagonists atenolol and LK 203-030 inhibited specific [125I]-(-)-cyanopindolol binding according to a one binding site model with low affinity in nearly all subjects, pointing to a homogeneous beta 2-adrenoceptor population. In one subject using LK 203-030 a small beta 1-adrenoceptor subpopulation could be demonstrated. The beta-mimetics isoprenaline, fenoterol, salbutamol and terbutaline recognized high and low affinity agonist binding sites. Isoprenaline's pKH- and pKL-values for the high and low affinity sites were 8.0 +/- 0.2 and 5.9 +/- 0.3 respectively. In functional experiments isoprenaline relaxed tracheal smooth muscle strips having intrinsic tone with a pD2-value of 6.63 +/- 0.19.