Effects of Stress Hormone Epinephrine and Activation of Protein Kinase A on the Osmotic Stability and Functional Parameters of Red Blood Cells From Marsh Frog

General stress-response of vertebrates to fluctuations of environmental conditions are conservative, and includes rapid release of neurotransmitters into blood. In amphibians, physiological effects of catecholamines (CA) on red blood cell (RBC) functions have been studied fragmentally despite the presence of adrenoreceptors on RBC membranes. In the present work the influence of epinephrine on RBC stability to hypoosmotic stress as well as intracellular reactive oxygen species (ROS) production levels and mitochondrial membrane potential have been studied on RBCs of marsh frogs Pelophylax ridibundus (in vitro). Additionally, the involvement of cAMP/Adenylate cyclase/protein kinase A (cAMP/AC/PKA) pathway in regulation of these processes have been evaluated. We showed that increase of RBC stability to hypoosmotic shock is mediated by activation of β-adrenoreceptors and independent from cAMP/PKA pathway. Lysis of RBCs treated with epinephrine occurred at lower osmolarities compared to non-stimulated cells and changes in RBC membrane properties were rapid (after 5 min incubation) and stable (following 60 min incubation). Addition of epinephrine to RBC suspensions or activation of cAMP/AC/PKA pathway (forskolin and cBIMPS) was associated with a reduction of ROS concentration in cytoplasm and enhanced mitochondrial membrane potential. The results of the present work provide novel insights into the cellular mechanisms of adrenergic RBC stimulation and pathways involved into signal transduction within the context of environmental stress. Stimulating effects of epinephrine on RBC membrane stability and mitochondrial activity is probably important for adaptation of frogs to unfavorable habitat conditions, seasonal activity and other stress factors.