Voltage clamp study of stimulant-evoked currents in mouse pancreatic acinar cells

Isolated segments of mouse pancreas were placed in a perspex bath and superfused with physiological saline solution. Acinar units were voltage-clamped with the help of two intracellular microelectrodes. Voltage homogeneity was in some experiments checked with a third microelectrode inserted into the same unit. The currents associated with hyper- or depolarizing voltage jumps were recorded in the absence or presence of sustained stimulation with acetylcholine (ACh), caerulein or bombesin nonapeptide. ACh (2 x 10(-7)-10(-8) M) evoked a dose-dependent inward current and an increase in the membrane conductance. The steady state ACh-evoked current (control current subtracted from total current in presence of ACh) depended linearly on voltage within the range -100 to +20 mV and its polarity reversed at about -25 mV. The effects of caerulein and bombesin nonapeptide were indistinguishable from those of ACh. Voltage homogeneity in the acinar unit was attained earlier than 1 ms after a hyper- or depolarizing voltage jump. The current transients associated with voltage jumps decayed according to single exponential functions both in the absence and presence of ACh. The time constant of the single exponential current decay after a voltage jump was the same (1-3 ms) in the absence or presence of ACh. The amplitude of the current transient was, however, reduced by ACh. The time constant of the current decay following voltage jumps was independent of the voltage in the range +60 to -60 mV, both in the absence and presence of ACh. The ACh-evoked reduction in the amplitude of the transient current following voltage jumps dependent linearly on the voltage.(ABSTRACT TRUNCATED AT 250 WORDS)