HYPERBARIC OXYGEN TREATMENT MODIFIES THE MECHANISMS ELICITING VASORELAXATION TO ACETYLCHOLINE IN FEMALE DIABETIC RATS
Abstract number: O29
Hyperbaric oxygen treatment (HBOT) has been demonstrated to improve ischemic vascular injury present in DM. There are only few functional studies regarding on altered vascular reactivity in female animal models of DM (and in women). We aimed to elucidate the effects of HBOT on the impaired acetylcholine-mediated (ACh) relaxation in aortic rings of female rats.
Four groups of female rats (12 week-old+6 weeks diabetes, 46 rats per group) were studied: control, streptozocin-diabetic, streptozocin-diabetic rats that underwent HBOT, and control rats that underwent HBOT. HBOT-treatment was at 2.0 atm, for 120 min for 4 days. Responses to cumulative concentration of acetylcholine (10-1010-5 M) in phenylephrine-precontracted aortic rings were measured with or without indomethacin, L-NAME or clotrimazol. Statistics were done as appropriate.
Relaxations of aortic rings of female DM rats in response to ACh was impaired, whereas ACh-mediated relaxation in diabetic-HBOT female rats was restored, compared to control rats, and to diabetic group, respectively. After L-NAME administration ACh-mediated relaxation was still partially preserved in DM-HBOT rats, while L-NAME eliminated ACh-relaxation in three other groups of rats. However, treatment with clotrimazol reduced ACh-mediated relaxation in control-HBOT rats compared to vessels of control rats, and reduced relaxations in DM-HBOT rats compared to DM rats. In all groups except DM rats, there were no significant differences in ACh-induced relaxations after indomethacin treatment. However, indomethacin improved relaxation in DM rats compared to responses to ACh in vessels of DM rats.
We suggest that impaired relaxation to ACh of aortic rings of DM rats could be due to an increased production of a cyclooxygenase-derived vasoconstrictor metabolite. HBOT leads to restoration of vasorelaxation in response to ACh in DM, which could be due to a vasorelaxing metabolite(s) of arachidonic acid, produced by CYP450 epoxygenases. Thus HBOT may modulate the mechanisms eliciting vascular relaxation in female diabetic rats.
grant of Croatian Ministry of Science, Education and Sport #219-2160133-2034.