Fig 4.
PMA facilitates exocytosis in gonadotropes by increasing the calcium sensitivity of release without significantly altering RRP size. (A) Averaged Cm responses for control (filled symbols) and PMA (100 nM, open symbols) treated gonadotropes, summarizing experiments that had postflash [Ca2+]i values between 4 and 6 μM. Superimposed curves are single exponential fits with the rate constants indicated. (B) PMA increases the Ca2+ sensitivity of release (all experiments plotted individually). Rate constants for exponential fits of the exocytotic burst are plotted against calcium levels for control (filled triangles), PMA-treated (open triangles, 100 nM for 2–3 min), and GnRH-treated (asterisks, 5 nM for 2 min) gonadotropes, respectively. The continuous curves represent the equation: Rate = R/(1 + (Kd/[Ca2+]i)3). (C) RRP size is unchanged by PMA or GnRH preincubation.