Distribution and properties of cardiac and pulmonary ß-adrenergic receptors in corn snakes (Pantherophis guttatus) and Boa constrictor (Boa constrictor).

The aim of the present study was to characterize ß-adrenergic receptors in the snake heart and lung of corn and Boa constrictor snakes. The ß-adrenergic receptor binding sites were studied in purified heart and lung membranes using the specific ß-adrenergic receptor antagonist [125J]-iodocyanopindolol (ICYP) and subtypes using selective ß1-adrenergic receptor antagonist CGP-20712A and selective ß2-adrenergic receptor antagonist ICI-118.551. A saturable and specific ß-adrenergic receptor binding site was detected in cardiac membranes with maximal receptor density (Bmax) of 43.99 ±â€¯3.86 fmol/mg protein (corn snake) and 58.07 ±â€¯2.88 fmol/mg protein (Boa constrictor) as well as KD of 24.21 ±â€¯7.38 pM (corn snake) and 21.48 ±â€¯3.85 pM (Boa constrictor) and in lung membranes (Bmax fmol/mg protein: 55.95 ±â€¯16.28 (corn snake) and 107.00 ±â€¯14.21 (Boa constrictor); KD pM: 71.25 ±â€¯21.92 (corn snake) and 55.04 ±â€¯18.68 (Boa constrictor)). Competition-binding studies showed ß-adrenergic receptors with low affinities to the ß2-selective adrenergic receptor antagonist and high affinity binding to ß1-selective adrenergic receptor antagonist in both heart and lung tissues of both snake species, suggesting the presence of high population of the post-synaptic ß1-adrenergic receptor subtype. It seems that the presence of the predominant ß1-subtype also in lung tissues may indicate the importance of the vascular system in the snake lung.