Adrenergic stimulation of rat resistance arteries affects Ca 2 1 sparks , Ca 2 1 waves , and Ca 2 1 oscillations

Mauban, Joseph R. H., Christine Lamont, C. William Balke, and W. Gil Wier. Adrenergic stimulation of rat resistance arteries affects Ca21 sparks, Ca21 waves, and Ca21 oscillations. Am J Physiol Heart Circ Physiol 280: H2399–H2405, 2001.—Confocal laser scanning microscopy and fluo 4 were used to visualize local and whole cell Ca21 transients within individual smooth muscle cells (SMC) of intact, pressurized rat mesenteric small arteries during activation of a1-adrenoceptors. A method was developed to record the Ca21 transients within individual SMC during the changes in arterial diameter. Three distinct types of “Ca21 signals” were influenced by adrenergic activation (agonist: phenylephrine). First, asynchronous Ca21 transients were elicited by low levels of adrenergic stimulation. These propagated from a point of origin and then filled the cell. Second, synchronous, spatially uniform Ca21 transients, not reported previously, occurred at higher levels of adrenergic stimulation and continued for long periods during oscillatory vasomotion. Finally, Ca21 sparks slowly decreased in frequency of occurrence during exposure to adrenergic agonists. Thus adrenergic activation causes a decrease in the frequency of Ca21 sparks and an increase in the frequency of asynchronous wavelike Ca21 transients, both of which should tend to decrease arterial diameter. Oscillatory vasomotion is associated with spatially uniform synchronous oscillations of cellular [Ca21] and may have a different mechanism than the asynchronous, propagating Ca21 transients.