The diving reflex (DR) is a defense mechanism that evolved during adaptation to diving in secondary amniotes and humans. The adaptive cardiovascular response of the diving reflex is achieved through reflexive deceleration of the heart's rhythm, constriction of peripheral vessels (PVs) and selective redistribution of blood to those organs which are most vulnerable to hypoxia (the brain, heart, lungs). This is achieved by a complex interaction of cholinergic and adrenergic influences of higher and autonomous mechanisms of regulation of the heart and blood vessels.
The aim of this study is to determine the dynamics of the reactions of the cardiovascular system during the implementation of the DR in subjects with different polymorphisms of the ADRB2 gene (p.Gly16Arg / rs1042713 / and p.Gln27Glu / rs1042714 /).
103 volunteers (students; aged 18-24) were examined. These subjects were not adapted to diving. DR was activated by submerging their faces in cold water (12-14◦C) under laboratory conditions. ECG records were taken for the resting state, during diving simulation and after apnea. The minute volume of blood flow (MVBF) was also determined for these states using rheography, and the blood supply to peripheral vessels was measured indirectly using the pulse wave amplitude (PWA) of the photoplethysmogram (PPG). Vascular tone was calculated from the time of its spread (the pulse transit time, PTT). Blood pressure was recorded. DNA samples from all patients’ blood were isolated using phenol-chloroform extraction. ADBR2 polymorphisms (p.Gly16Arg / rs1042713 / and p.Gln27Glu / rs1042714 /) were investigated using two-stage multiplex PCR followed by hybridization of alleles on a biochip. The results were analyzed using Mann-Whitney nonparametric tests (paired comparisons).
On the whole, in the group of the subjects, during the implementation of the DR, a statistically significant decrease in heart rate, MVBF, PWA, indirectly reflecting the narrowing of peripheral vessels, as well as an increase in systolic and diastolic pressure is observed. No statistically significant change in stroke blood volume was found. In subjects with A/A (p.Gly16Arg) and C/C (p.Gln27Glu) polymorphisms of the ADRB2 gene during diving simulation, a statistically significant decrease in the PWA is observed, which indirectly reflects the tone of resistive peripheral vessels; In subjects with polymorphisms G/A (p.Gly16Arg) and C/G, G/G (p.Gln27Glu), no significant changes in this indicator were found during diving simulation. In subjects with polymorphisms with G/A and G/G (p.Gly16Arg) and C/C, G/C (p.Gln27Glu) of the ADRB2 gene, a statistically significant decrease in heart rate and a decrease in the MVBF were observed during diving simulation.
Thus, not only the constrictor function of the vessels, but also the chronotropic function of the heart, reflexively realized in the test with diving simulation, significantly differs in those examined with different polymorphisms of the ADRB2 gene. The most pronounced constriction is observed in those examined with A/A p.Gly16Arg and C/C p.Gln27Glu, and slowing of heart rate in those examined with polymorphisms G/A and G/G p.Gly16Arg and C/C, G/C p.Gln27Glu of the ADRB2 gene.
