Repeated immobilization stress decreases mRNA and protein levels of the type 1 IP3 receptor in rat heart.

Stress is one of the major contributors to the development of cardiovascular disorders and psychiatric illnesses. Immobilization stress belongs to severe stressors and is known to activate several calcium transport systems. The aim of this work was to determine whether repeated immobilization stress changes mRNA and protein levels of the type 1 and 2 inositol-1,4,5-trisphosphate (IP(3)) receptors in cardiac tissue. Rats were immobilized for 7 days, 2 h daily. After repeated immobilization, increased numbers of collagen fibers were accumulated in the heart atria compared to hearts of the control group of rats. Gene expression was determined after reverse transcription and subsequent real-time polymerase chain reaction, using SYBR Green fluorescent dye. Protein levels were determined by Western blot and hybridization with the primary antibody against IP(3) receptors. Contrary to single immobilization, repeated immobilization decreased a gene expression of the type 1 and 2 IP(3) receptors, and also protein levels of the IP(3) receptors. Although the physiologic relevance of our observations remains to be elucidated, we propose that the decrease in IP(3) receptors may have an impact on the development of the pathophysiologic changes in the heart.