engleski

Vascular relaxation to acetylcholine in female diabetic rats that underwent hyperbaric oxygenation ; the role of EETs and 20-HETE

Introduction: Impaired vascular relaxation has been described previously in diabetes mellitus (DM), mostly in male. A few functional studies were made in female animal models of DM or in diabetic women. 20-HETE (20 - hydroxyeicosatetraenoic acid) and epoxyeicosatrienoic acids (EETs) play an important role in the regulation of vascular tone, production of which increases with increase in pO2 (1). Hyperbaric oxygenation (HBO) is used successfully in therapy of chronic vascular complications of DM ; however, the mechanisms of its action are not clarified yet. Aims: This study aimed to elucidate relaxation mechanisms in response to acetylcholine (ACh) in aortic rings of DM female rats, exposed to HBO and to determine the possible role of 20-HETE and EETs in that response. Methods: Female Sprague-Dawley rats (12 weeks-old at the time of experiment, 6 weeks DM duration) were divided into 4 groups: control group, DM group, and control-HBO rats and DM-HBO rats that underwent HBO (120 minutes in duration, at 2, 0 atm for 4 consecutive days). Prior to decapitation, rats were anesthetized with Ketanest (ketamine, generic name 75 mg/kg) and midazolam (2.5 mg/kg) intraperitoneally. N= 9-18 rings/per group/treatment. Vascular responses to cumulative concentration of ACh (10-10 to 10-5M) in nerepinephrine-precontracted aortic rings were measured with/without L-NAME, clotrimazol (CYP450 epoxygenase inhibitor) or HET0016 (CYP450-omega hydroxylase inhibitor) and to endothelium- independent NO donor, sodium-nitropruside (SNP). The data are presented as mean ± SD and analyzed with Two-way ANOVA Repeated Measures and Bonferroni posttest ; p&lt ; 0, 05 was considered to be statistically significant. The study was approved by the Ethical Committee of Faculty of Medicine University of Osijek. Results: Basal ACh response was preserved in all groups of rats, possibly due to short duration of DM. However, administration of HET0016, selective inhibitor of 20-HETE production, increased vasorelaxation to ACh in DM-HBO compared to DM rats, while clotrimazol significantly reduced relaxation in response to ACh in control-HBO rat and DM-HBO rats compared to their respective controls. L-NAME significantly decreased ACh-induced dilation in all groups of rats. Relaxation in response to SNP was slightly reduced in DM group compared to DM- HBO group. Conclusions: These results suggest that HBO could affect the mechanisms of relaxation response to ACh in both, control-HBO and DM-HBO treated rats. ACh-induced relaxation could be mediated not just with NO, but also with partial contribution of EETs, in both control-HBO and DM- HBO rats. Enhanced relaxation after blockade of 20-HETE production in DM-HBO rats suggest its' contribution to vascular tone under the HBO treatment in female diabetic rats.

hyperbaric oxigenation; diabetes

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