Figure 7. Reduced STOC/spark coupling as a factor contributing to an increased vascular tone in diabetic CASMCs. A.

. Estimated STOC/Spark coupling ratio in control (white bar) and db/db (orange bar) CASMCs. The estimated coupling ratio was obtained by dividing the frequency of STOCs in each cell (n = 11 control vs n = 10 db/db cells) at near resting membrane potential (−40 mV) between the average frequency of spontaneous Ca²⁺ sparks in single quiescent cells; *P<0.05. B. Schematic representation of single db/db CASMC where the triggering of STOCs is not tightly controlled by Ca²⁺ sparks. The decreased STOC/Spark coupling ratio suggests that most of the Ca²⁺ sparks produced in the diabetic cells are STOCless having a detrimental impact on the regulation of vascular myogenic tone. SERCA: sarco/endoplasmic reticulum Ca²⁺ ATPase, BK: big conductance Ca²⁺-activated K⁺ Channel, VDCC: L-type Ca²⁺ channel, RyR: ryanodine receptor.