Fig. 1. Cytosolic calcium [Ca²⁺]_i response of rectal gland artery (RGA) segments to varying concentrations of external calcium [Ca²⁺]_e. Each data point is part of paired observations in which at least two concentrations of calcium were tested with each RGA sample. Between [Ca²⁺]_e concentrations of 0.8 and 5.3 mmol l^-1, there was a linear concentration response between [Ca²⁺]_i and [Ca²]_e (r²=0.51, P<0.01).