Effect of nifedipine and dipyridamole on K+ and NA stimulated 45Ca-uptake into rabbit aortic strips.

The effect of dipyridamole (DPM), a purine nucleoside uptake inhibitor, on the K+ and noradrenaline (NA)-stimulated 45Ca-uptake into Rabbit aortic strips was studied and compared with that of nifedipine (NFD). DPM (10(-6) M) significantly (P < 0.02) inhibited 45Ca-uptake in aortic strips stimulated with K+ (10(-1) M). However, it had less significant effect on NA (10(-4) M)-stimulated 45Ca-uptake. The percentage inhibition was 80 and 57 in K+ and NA-stimulated 45Ca-uptake, respectively. Similarly, NFD (10(-7) M) caused significant (P < 0.01, P < 0.05) decrease in K+ (0.060 +/- 0.009) and NA (0.082 + 0.01, mM)-stimulated 45Ca-uptake. The percentage inhibition by NFD was 98 and 64 in K+ and NA-stimulated 45Ca-uptake, respectively. The results suggest that DPM inhibits Ca2+ influx occurring through Voltage Operated Calcium Channels (VOCCs) but it has little effect on Receptor Operated Calcium Channels (ROCCs).