Table II.

Inhibitor concentrations that cause 50% inhibition (I₅₀) of Ca²⁺ uptake in Golgi vesicles

Inhibitor	I50
Thapsigargina	88 nm
Cyclopyazonic acid	0.36 nmol mg−1
Na vanadatea	126 μm

^a Protein concentration in Golgi apparatus fraction was 600 μg mL⁻¹. The range of inhibitor concentrations tested were: thapsigargin, from 0.1 to 3,000 nm; cyclopiazonic acid, between 0.01 and 100 nmol mg⁻¹; and vanadate, from 0.01 to 10,000 μm. Free Ca²⁺ concentration was 870 nm. Values are mean ± se of three different experiments in triplicate.