December 2002
Volume 43, Issue 13
Free
ARVO Annual Meeting Abstract  |   December 2002
LY379196 Reverses Attenuated Store-operated Calcium Influx in Retinal Microvessels From Diabetic Rats
Author Affiliations & Notes
  • TM Curtis
    Department of Ophthalmology
    Queen's University of Belfast Belfast United Kingdom
  • E Major
    Smooth Muscle Group
    Queen's University of Belfast Belfast United Kingdom
  • CN Scholfield
    Smooth Muscle Group
    Queen's University of Belfast Belfast United Kingdom
  • Footnotes
    Commercial Relationships   T.M. Curtis, None; E. Major, None; C.N. Scholfield, None. Grant Identification: Supported by the Wellcome Trust and British Heart Foundation
Investigative Ophthalmology & Visual Science December 2002, Vol.43, 1335. doi:
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      TM Curtis, E Major, CN Scholfield; LY379196 Reverses Attenuated Store-operated Calcium Influx in Retinal Microvessels From Diabetic Rats . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1335.

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Abstract

Abstract: : Purpose: In diabetes, hyperglycemia leads to a deterioration in retinal microvascular function and there is now strong evidence that the persistent upregulation of PKCß might be partially responsible. Ca2+ signalling in response to vasoconstrictors is blunted in retinal vessels from diabetic rats and the present work aimed to assess the role of store-operated Ca2+ (SOC) entry in this phenomenon and the effects of PKC antagonists. Methods: Sprague-Dawley rats (200-230g) were given 60mg kg-1 streptozotocin I.P. and killed 4-6 weeks later. Animals with blood glucose concentrations ≷15 mM were taken as diabetic (mean glucose 29 ± 2.2 mM). Injected animals with glucoses <7 mM were used as non-diabetic controls (mean glucose 5.5 ± 0.4 mM). Cytosolic Ca2+ was estimated from freshly isolated rat retinal arterioles using fura-2 microfluorimetry. In vessels from diabetic animals, 25 mM D-glucose was present through the isolation procedure and experiment. SOC influx was assessed by depleting Ca2+ stores with Ca2+ free/cyclopiazonic acid over 10 min and subsequently measuring the rise in Ca2+ over the initial 10 s on adding 2 mM Ca2+ solution. At least 4 rats were used per treatment group. Comparisons used the unpaired t-test. Results: SOC influx was attenuated in vessels from diabetic rats: in non-diabetic vessels the addition of 2 mM Ca2+ induced a mean rate of rise in Ca2+ of 7.4 nM s-1 (n=17) compared with 3.2 nM s-1 (n=18) in vessels from diabetic animals (P=0.007). In vessels from non-diabetics 25 mM D-mannitol had no effect on SOC entry, consistent with a non-osmotic mechanism (P=0.8; n=8). Diabetic animals injected daily with insulin (protamine-zinc, 5 units) for 2 weeks had a mean blood glucose of 3.5 ± 1 mM and SOC influx similar to non-diabetic controls (P=0.48; n=10). The reduced SOC entry in diabetic vessels was reversed by 2 h exposure to 100 nM staurosporine (SP), a non-specific PKC antagonist (P = 0.0006, paired comparison with and without SP in the same animals; n=14) and by the specific PKCß antagonist LY379196 (100 nM; P=0.02 using the same experimental design as for SP; n=10). Conclusion: These results demonstrate that SOC influx is inhibited in retinal arterioles from animals having sustained elevated blood glucose and that PKCß appears to play a major role in mediating this effect.

Keywords: 334 calcium • 387 diabetes • 614 vascular cells 
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