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Voltage independence of vasomotion in isolated irideal arterioles of the rat

Date

2002

Authors

Haddock, Rebecca
Hirst, G D S
Hill, Caryl

Journal Title

Journal ISSN

Volume Title

Publisher

Cambridge University Press

Abstract

The cellular mechanisms underlying vasomotion of irideal arterioles from juvenile rats have been studied ng electrophysiological methods, ratiometric calcium measurements and video microscopy. Vasomotion was not affected by removal of the endothellium. Spontaneous contractions were preceded by spontaneous depolarizations. Both were abolished by the intracellular calcium chelator, BAPTA AM (20 μM), but not by ryanodine (10 μM), suggesting a dependence on the cyclical release of calcium from intracellular stores, other than those operated by ryanodine receptors. Oscillations were little changed when the membrane potential of short segments of arteriole was either depolarized. or hyperpolarized. When the segments were voltage damped, oscillating inward currents were recorded, indicating that the changes in membrane potential were voltage independent. Vasomotion was preceded by intracellular calcium oscillations and both were abolished by inhibitors of phospholipase C (U73122, 10 μM), phospholipase A2 (AACOCF3, 30 μM) and protein kinase C (chelerythrine chloride, 5 μM, and myristoylated protein kinase C peptide, 10 μM). Inhibition of vasomotion by the dual lipoxygenase and cyclo-oxygenase inhibitor, NDGA (10 μM), the lipoxygenase inhibitor, ETI (1 μM) but not by the cyclo-oxygenase inhibitors, aspirin (10 μM) and indomethacin (10 μM), or the cytochrome P450 inhibitor 17-ODYA (10 μM), suggested an involvement of the lipoxygenase pathway. The observations suggest that vasomotion of iris arterioles is voltage independent and results from the cyclical release of calcium from IP3-sensitive stores which are activated by cross talk between the phospholipase C and phospholipase A2 pathways in vascular smooth muscle.

Description

Keywords

Keywords: 1 [[6 (3 methoxyestra 1,3,5(10) trien 17beta yl)amino]hexyl] 1h pyrrole 2,5 dione; 17 octadecynoic acid; acetylsalicylic acid; arachidonyl trifluoromethyl ketone; calcium chelating agent; calcium ion; chelerythrine; cytochrome P450 inhibitor; ethylene gly

Citation

Source

Journal of Physiology

Type

Journal article

Book Title

Entity type

Access Statement

License Rights

DOI

10.1113/jphysiol.2001.013698

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