Figure 5. Electrophysiological properties of converted α-cells.

(a) Voltage-dependent inactivation of Na⁺ channels is left-shifted in control β-cells (red; n=9) compared with control α-cells (black; n=13). Total mice = 3.

(b) Inactivation of Na⁺ currents in non-converted (Ins^Neg,YFP⁺) αiADKO α-cells (black; n=21, mice = 3) was identical to the control α-cells, while the majority (~70%) of Na⁺ current inactivation in the converted (Ins⁺,YFP⁺) αiADKO β-cells (red; n=27, mice = 3) was left-shifted similar to that observed in β-cells.

(c–j) Single-cell exocytosis was measured by monitoring capacitance increases in response to a series of membrane depolarizations following transition from 20 to 2 mM glucose (black) or from 2 to 20 mM glucose (red). Representative traces (c,e,g) and averaged data (d,f,h) are shown. In control α-cells (c,d), exocytosis was amplified by lowering glucose (n=21, mice = 2) and suppressed by raising glucose (n=16, mice = 2). Identical results were observed (e,f) in non-converted (Ins^Neg,YFP⁺; inset) αiADKO α-cells (n=13 and 24, mice = 3). In control β-cells (g,h), exocytotic response was amplified by raising glucose (n=8) and suppressed by lowering glucose (n=6, mice=2). In converted (i,j; Ins⁺,YFP⁺ ; inset) αiADKO α-cells, however, the response was reversed to recapitulate a β-cell phenotype such that raising glucose amplified the exocytotic response (n=23, mice = 3) while lowering glucose suppressed it (n=14). * P<0.05; ** P<0.01; *** P>0.001.