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RESEARCH ARTICLE
SA JOURNAL OF DIABETES & VASCULAR DISEASE
28
VOLUME 14 NUMBER 1 • JULY 2017
blunted adrenergic responses observed in the presence of glitazones
were mediated by the action of these drugs on the endothelial cells,
since the effect disappeared when the endothelium was removed
in a study Mendizabal and co-workers.
21
Conclusion
In this study,
in vitro
experiments were carried out to investigate
the direct effect of pioglitazone and/or losartan on aortic rings
of control, diabetic, hypertensive and hypertensive diabetic rats.
Our results demonstrate that vascular sensitivity to an alpha
adrenoceptor agonist was decreased in the presence of pioglitazone
and/or losartan in diabetic and/or hypertensive rat aortic rings. We
postulate that these results explain at least in part the beneficial
effects of pioglitazone and losartan for hypertension and diabetes.
The mechanism of action of pioglitazone and losartan to improve
vascular reactivity may be as a result of intracellular protection from
oxygen free radicals. Our findings suggest a possible beneficial
combination of thiazolidinediones and angiotensin receptor
blockers for treatment of diabetes and hypertension.
Further studies are required to elucidate the effects of
pioglitazone and losartan on alpha receptors and on the mediators
of NO metabolism. It is also remains unclear how pioglitazone
and losartan inhibited alpha-2 receptor activities in our rat aortic
rings. Further investigation is needed to clarify these underlying
mechanisms.
Acknowledgements
This study was supported by research funding fromADU (TPF09019).
We thank Santek Medikal (Izmir, Turkey) for generously donating
the IME-DC
®
Glucometer (GmbH, Germany) and Sandoz (Istanbul,
Turkey) for the pioglitazone.
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