ABSTRACT
It has been shown in the rat that insulin affects expression of the rat equilibrative nucleoside transporter [rENT] 2 and rat concentrative nucleoside transporter [rCNT] 1 and 2 in cardiac fibroblasts and adenosine uptake by cardiac myocytes. The aim of this study was to explore the effects of streptozotocin [STZ]-induced diabetes in the rat heart on the expression of rENTl and 2 and rCNTl, 2 and 3. Diabetes was induced in Sprague-Dawley rats by an i.p. injection of STZ [60 mg/kg]; controls were treated with vehicle. Diabetes was confirmed by plasma glucose >17 mM. Rats were sacrificed after 4 weeks, and cardiac muscle samples were frozen in liquid N[2]. Real-time PCR was used to estimate the threshold cycles for target amplification [Ct] values. The differences between the Ct values for ENTs and CNTs and the Ct values for the housekeeping gene [3-actin were calculated [Act], and the difference between diabetic and control rats was tested for significance. Data are presented as mean +/- SD from 3 samples. Results: The Ct value of [3-actin did not differ significantly between the groups [p > 0. 05], so this gene was used as the endogenous control. In the control group, the mRNA for rCNT2, rENT2, rENTl and rCNTl were detected with the Act 2.4 +/- 0.4, 4. 3 +/- 0.3, 7.4 +/- 0.6 and 8.1 +/- 0.1, respectively. The mRNA for rCNT3 was apparently absent. Four-week diabetes caused a significant decrease in the amount of mRNA for rCNTl [p < 0.05 vs. control], while the amount of mRNA for other transporters did not change significantly. The observed changes in the amount of rCNTl mRNA may indicate a decrease in the amount of this pyrimidine-selective transporter in the membrane, which in turn could reduce the cellular uptake of py-rimidines in diabetes