Fig. 6. Effect of ryanodine on intracellular Ca2+stores. ( A ) Dakiki cells in suspension were preexposed to normal Hanks balanced salt solution (HBSS) ( upper trace ), Ca2+-free HBSS ( middle trace ), or Ca2+-free HBSS plus 1 mm ryanodine ( lower trace ) for approximately 1 h. Cells were washed and resuspended in intracellular Ca2+–free HBSS, and 100 nm thapsigargin was applied at 30 s. Each trace represents a single experiment. ( B ) Measurement of thapsigargin-induced intracellular Ca2+release. Integral values determined from individual tracings, then averaged to yield mean ± SEM for control, 0 Ca2+, and 0 Ca2+plus ryanodine. Values were 108 ± 5 (n = 23), 89 ± 2 (n = 3), and 44 ± 10 (n = 3), respectively. * Ryanodine-treated cells were significantly different from those in 0 Ca HBSS alone ( P = 0.0124).