β-adrenergic receptors (β-ARs) play a pivotal role in the cardiovascular regulation. In the human heart β1- and β2-ARs dominate in atria as well as in ventricle influencing heart rate and myocardial contractility. Some single nucleotide polymorphisms (SNPs) of β-ARs might influence cardiovascular function. However, the influence of β-AR genes SNPs on hemodynamic parameters at rest and their reactivity under stress is still not well known. We aimed to explore the associations between four selected β-ARs gene polymorphisms and selected cardiovascular measures in eighty-seven young healthy subjects. While in β1-AR polymorphism rs1801252 no significant association was observed, second β1-AR polymorphism rs1801253 was associated with decreased cardiac output and cardiac index during all phases and with decreased flow time corrected and ejection time index at rest and during mental arithmetics. Polymorphism rs1042713 in β2-AR was associated with alterations in blood pressure variability at rest and during head-up-tilt, while rs1042714 was associated predominantly with decreased parameters of cardiac contractility at rest and during mental arithmetics. We conclude that complex analysis of various cardiovascular characteristics related to the strength of cardiac contraction and blood pressure variability can reveal subtle differences in cardiovascular sympathetic nervous control associated with β-ARs polymorphisms.
Changes in beta-adrenergic receptors in the neurohypophysis and intermediate lobe of the rat have been characterized under physiological and stress conditions. Classical immobilization stress (IMO) was also combined with the immersion of rats into water (IMO + COLD stress). Both types of stress were applied for 30, 60 or 150 min. The intensity of stress stimuli were controlled by measuring the level of plasma ACTH. Changes in the level of plasma ACTH indicate that both types of experimental protocol induced reliable and reproducible stress conditions. Binding studies dealing with beta-adrenergic receptors in the intermediate lobe and neurohypophysis were performed in saturation binding studies by using of 125l-iodopindolol. Binding parameters, maximal binding capacity (Bmax) and dissociation constant (Kd) were assessed by nonlinear analysis with computer program Viewfit. In the neurohypophysis, no changes of Kd were found in the stressed animals. However, maximal binding capacity was decreased significantly with the increased exposure to the stress. In the intermediate lobe Kd values were slightly decreased and Bmax values decreased gradually with increasing duration of stress exposure. Our findings suggest that the process of receptor desensitization of beta-adrenergic receptors can also be detected under stress conditions in the neurohypophysis and intermediate lobe of the pituitary gland where it could contribute to the mechanisms involved in stress reactions.