Figure 4.

Bimodal distribution of temporal acetylcholine (ACh) responses in rat pulmonary artery endothelium after store depletion. A: All groups display a robust increase in the number of Ca²⁺ events in responses to ACh relative to baseline. Counts of event duration per group [wild-type (wt), TRPC4-knockout (ko), wt pulmonary arterial hypertension (PAH), and TRPC4-knockout PAH] plotted as histograms reveal the existence of both long (gray bars) and short (black bars) duration modes of response. B: Signal envelopes of selected short- and long-duration cellular response were characterized by quick onset to peak fluorescence. Short responses exhibit rapid return to basal Ca²⁺ levels, whereas long responses show sustained and gradual decreases to baseline. C: The number of events of both short mode (left) and long mode (right) duration responses to ACh is not significantly affected by animal genotype or PAH; however, long-duration responses are completely abolished in both normotensive ko and wt PAH groups. D: In addition, the duration of short responses is significantly greater in normotensive ko and ko PAH groups compared with wt. The duration of long responses is attenuated in normotensive knockout animals, and significantly increased in PAH. n = 4 for all groups (C and D). ^∗∗P < 0.01.