Altered expression of adenosine receptors in heart of diabetic rat.

Diabetes results in functional, biochemical, and morphological abnormalities in the heart. Some of these changes may be attributed to altered adenosine action. This study aimed to examine the expression level of adenosine receptors (AR) in heart of streptozotocin-induced diabetic rat. Performed analyses revealed detectable levels of A1-AR, A2a-AR, A2b-AR, A3-AR mRNA and protein in whole heart and isolated cardiac myocytes. An increase in A1-AR protein content with no changes in mRNA level was observed in isolated cardiac myocytes. Diabetes resulted in an increase of A3-AR mRNA and protein levels in heart and in cardiac myocytes. The level of A2a-AR mRNA was increased in whole diabetic heart, but it decreased in cardiac myocytes with no detectable changes in protein content. We did not observe any changes in expression level of A2b-AR in diabetic heart and isolated cardiac myocytes. Administration of insulin to diabetic rat for four days resulted in returning of the ARs mRNA and protein to the levels observed in heart of normal rat. These changes in ARs genes expression, and receptors protein content correspond to some abnormalities characteristic of the diabetic heart, suggesting involvement in pathogenesis of diabetic cardiomyopathy.