Effects of acetylcholine and transport inhibitors on K content in dispersed submandibular salivary cells of newborn and adult rats.

These isolated cells were used to measure uptake of the radioactive tracer 86Rb as an index of changes in K+ content. There was time-dependent tracer uptake in the absence of secretagogue in both one-day-old and adult cells. Kinetic analysis of this uptake revealed two components, a fast one during the first 5 min of incubation and a slower one between 5 and 30 min. The early (fast) component was slower in the newborn cells (0.084 nmol mg-1 min-1) than in adult cells (0.116 nmol mg-1 min-1). Values for the second component of uptake were, respectively, 0.015 and 0.009 nmol mg-1 min-1. Basal uptake of K+ was inhibited by both ouabain and furosemide (at 1 mM concentrations) but, after 5 min of incubation, the effect was more pronounced in adult cells. The K+ content (i.e. K+ uptake) was increased after exposure to 1 microM acetylcholine in both cell types, but the effect was larger in those from one-day-old rats after 5 min incubation (16 per cent increase, compared to 9 per cent increase in adult cells). The secretagogue-induced increase in K+ uptake or content was inhibited by ouabain (57 per cent in adult cells, 24 per cent in newborn cells), and by furosemide (25 and 37 per cent, respectively). These findings suggest that K+ uptake in submandibular cells occurs by both an ouabain-sensitive Na, K pump and a diuretic-sensitive transport system. Both appear to have lower resting activities in the cells of newborn rats but can be significantly stimulated cholinergically.(ABSTRACT TRUNCATED AT 250 WORDS)