This study determined whether whole cell @entity141 transients and unitary sarcoplasmic reticulum (SR) @entity141 release events are constant throughout adult life or whether @entity141 release is altered in aging ventricular myocytes. Myocytes were isolated from young adult (approximately 5 mo old) and aged (approximately 24 mo old) @entity19 . Spontaneous @entity141 sparks and @entity141 transients initiated by field stimulation were detected with @entity20048 . All experiments were conducted at 37 degrees C. @entity141 transient amplitudes were reduced, and @entity141 transient rise times were abbreviated in aged cells stimulated at 8 Hz compared with young adult myocytes. Furthermore, the incidence and frequency of spontaneous @entity141 sparks were markedly higher in aged myocytes compared with young adult cells. Spark amplitudes and spatial widths were similar in young adult and aged myocytes. However, spark half-rise times and half-decay times were abbreviated in aged cells compared with younger cells. Resting cytosolic @entity141 levels and SR @entity141 stores were assessed by rapid application of @entity5834 in @entity593 -loaded cells. Neither resting @entity141 levels nor SR @entity141 content differed between young adult and aged cells. Thus increased spark frequency in aging cells was not attributable to increased SR @entity141 stores. Furthermore, the decrease in @entity141 transient amplitude was not due to a decrease in SR @entity141 load. These results demonstrate that alterations in fundamental SR @entity141 release units occur in aging ventricular myocytes and raise the possibility that alterations in @entity141 release may reflect age-related changes in fundamental release events rather than changes in SR @entity141 stores and diastolic @entity141 levels.

Calcium spark properties in ventricular myocytes are altered in aged XXXX .

@entity19 :: ('10090', 'Species') :: ['mice'] @entity5834 :: ('MESH:D002110', 'Chemical') :: ['caffeine'] @entity593 :: ('MESH:D016257', 'Chemical') :: ['fura-2'] @entity141 :: ('CHEBI:29108', 'Chemical') :: ['Ca(2+)'] @entity20048 :: ('MESH:C409648', 'Chemical') :: ['fluo-4']
@entity19 :: (10090,Species) :: ['mice']
