Background
—Previous data suggest that 1 endothelial NO synthase (eNOS) gene is sufficient to allow normal expression and function of eNOS under basal conditions. We hypothesized that this might not hold true for conditions known to increase eNOS gene expression, such as exercise.
Methods and Results
—Male mice heterozygous for a disruption of the eNOS gene (eNOS
+/
−
) and normal C56Bl/6J mice (eNOS
+/+
), 3 to 4 months of age, underwent exercise training for 3 weeks. Nontrained mice were exposed to the exercise environment (noise and vibration of the treadmill) without exercise for an identical period. In eNOS
+/+
mice (n=7), exercise increased aortic eNOS protein expression by 3.4±0.4-fold (
P
<0.002). This was associated with a greater vascular cGMP accumulation on stimulation with acetylcholine (
P
<0.05). Furthermore, exercise training increased eNOS mRNA (1.78±0.4-fold) and protein (1.76±0.17-fold) in left ventricular tissue, as determined by competitive reverse transcription–polymerase chain reaction and Western analysis (
P
<0.05 for both). In striking contrast, exercise had no effect on aortic eNOS expression and cGMP accumulation in eNOS
+/
−
mice (
P
>0.05). Thus, although eNOS expression appears to be normal in eNOS
+/
−
mice under basal conditions, these mice are unable to increase eNOS expression during exercise.
Conclusions
—These findings show that regulation of eNOS expression during exercise requires the presence of both alleles of the gene and may have implications for conditions in which polymorphisms of eNOS are present in only 1 allele in humans. These individuals may have a normal vascular reactivity under basal conditions but may be unable to adapt their vascular reactivity in response to exercise training.
Current retinal prosthetics are designed to stimulate existing neural circuits in diseased retinas to create a visual signal. However, implantation of retinal prosthetics may create a neurotrophic environment that also leads to improvements in visual function. Possible sources of increased neuroprotective effects on the retina may arise from electrical activity generated by the prosthetic, mechanical injury due to surgical implantation, and/or presence of a chronic foreign body. This study evaluates these three neuroprotective sources by implanting Royal College of Surgeons (RCS) rats, a model of retinitis pigmentosa, with a subretinal implant at an early stage of photoreceptor degeneration. Treatment groups included rats implanted with active and inactive devices, as well as sham-operated. These groups were compared to unoperated controls. Evaluation of retinal function throughout an 18 week post-implantation period demonstrated transient functional improvements in eyes implanted with an inactive device at 6, 12 and 14 weeks post-implantation. However, the number of photoreceptors located directly over or around the implant or sham incision was significantly increased in eyes implanted with an active or inactive device or sham-operated. These results indicate that in the RCS rat localized neuroprotection of photoreceptors from mechanical injury or a chronic foreign body may provide similar results to subretinal electrical stimulation at the current output evaluated here.
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