Table 1. Glucose dependence of three GLP-1 concentrations on [Ca²⁺]_i.

Only cells exhibiting a ≥ 75 nm increase of [Ca²⁺]_i were counted as exhibiting a response to GLP-1. The increase of [Ca²⁺]_i was measured at the peak of the response. Base-line levels of [Ca²⁺]_i were 91 ± 8 nm (n = 50). Except where indicated, the extracellular solution contained 0.8 mm glucose. To deprive the cells of glucose, cultures were preincubated in glucose-free recording solution for 1 h at 37 °C. GLP-1 was applied directly to individual cells for 30 s using a puffer pipette. Data summarize results obtained in two experiments using βTC6 cells from two different platings.

[GLP-1(7-37)]	Fraction of βTC6 cells responding to GLP-1(7-37)	Mean ± S.D. increase of [Ca2+]i
nm		nm
With 0.8 mm
d-glucose
0.1	3/10	207 ± 55
1.0	6/10	295 ± 87
10	8/10	386 ± 73
Without
d-glucose
0.1	0/10
1.0	0/10
10	2/10	267 ± 69