Travis W. Hein

Learn More
PURPOSE Lactate, a key metabolite in the retinal tissue, has been implicated in regulating retinal blood flow to match retinal metabolic demand. However, the direct effect of lactate on retinal vascular tone and the possible underlying signaling mechanisms remain unknown. In the present study, the roles of endothelium-derived vasodilators, guanylyl cyclase,(More)
Arginase shares a common substrate, L-arginine, with nitric oxide (NO) synthase (NOS). It is thought that arginase, if it is expressed in the endothelium, might play a pivotal role in the regulation of NO-mediated vasodilation by reducing the L-arginine availability to NOS. In the present study, we wanted to determine whether arginase is expressed and(More)
PURPOSE Although the arteriolar segment contributes to flow regulation, there is sparse information at the single microvessel level on how vasomotor function is regulated in the human retina. The authors have previously reported vasoreactivity and its underlying mechanisms in isolated porcine retinal arterioles. Herein, they studied human retinal arterioles(More)
PURPOSE Adenosine is a potent vasodilator of retinal microvessels and is implicated to be a major regulator of retinal blood flow during metabolic stress. However, the receptor subtypes and the underlying signaling mechanism responsible for the dilation of retinal microvessels in response to adenosine remain unclear. In the present study, the roles of(More)
One characteristic of hypertension is a decreased endothelium-dependent nitric oxide (NO)-mediated vasodilation; however, the underlying mechanism is complex. In endothelial cells (ECs), L-arginine is the substrate for both NO synthase (NOS) and arginase. Because arginase has recently been shown to modulate NO-mediated dilation of coronary arterioles by(More)
Oxidized LDLs (Ox-LDLs) inhibit endothelium-dependent dilation of isolated conduit arteries in a manner comparable to the impairment demonstrated in atherosclerotic vessels. However, it is not known whether the microvessels, which do not develop atherosclerotic lesions, are susceptible to Ox-LDL. Since endothelial release of NO plays an important role in(More)
PURPOSE Resveratrol, a polyphenolic phytoalexin found in grapes and red wine, has been shown to exert cardiovascular benefits, but its action in the retinal microcirculation remains unknown. In this study, the direct effect and the underlying mechanism of the vasomotor action of resveratrol were examined in retinal arterioles. METHODS Porcine retinal(More)
PURPOSE Elevated levels of C-reactive protein (CRP), a proinflammatory marker, are associated with systemic vascular disorders. In addition, clinical studies have implicated that elevated CRP is an independent risk factor for diabetic retinopathy and age-related macular degeneration. However, the direct effect of CRP on ocular microvascular reactivity(More)
PURPOSE Results in a prior study have demonstrated that systemic administration of the 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitor simvastatin to healthy subjects reduces intraocular pressure and increases retinal blood flow. However, it remains unclear whether simvastatin can directly elicit dilation of retinal microvessels. In the(More)
PURPOSE Although hyperglycemia is implicated in retinal vascular dysfunction associated with the development of diabetic retinopathy, the temporal influence of hyperglycemia on retinal arteriolar reactivity remains unclear. Development of a large animal model of diabetes relevant to the human retina for evaluation of vascular function is also lacking.(More)