Abstract
A pancreatic acinar cell line, AR4–2J, that expresses a high density of substance P (SP)-binding sites has been identified. SP-binding sites on intact AR4–2J cells were detected with 125I-Bolton-Hunter SP (125I- BHSP). 125I-BHSP binding to AR4–2J cells has an apparent Kd of 40 pm with slow rates of association and dissociation. The number of high affinity binding sites was about 10(4)/cell. Binding of 125I-BHSP was inhibited by SP and by structurally related peptides. Physalaemin was a more potent inhibitor of binding than SP, whereas kassinin, eledoisin, and neurokinin A (substance K, neuromedin alpha, or neurokinin L) were much less potent. SP-free acid and SP (7–11) were 3 to 4 orders of magnitude less potent than SP itself. The membrane, intracellular, and secretory events elicited by exposure of AR4–2J cells to SP have also been examined. Intracellular recording from AR4–2J cells revealed resting membrane potentials of -40 to -65 mV. Pressure application of SP (100 pM to 100 nM) evoked depolarizations of 20 to 40 mV which were maintained for prolonged periods. The intracellular free calcium concentration in AR4–2J cells, measured with (2-[2-amino-5- methylphenoxy)-methyl)-6-methoxy-8-aminoquinolone tetra-acetoxy methyl ester), was between 100 and 500 nM. Addition of SP (100 pM to 10 nM) or physalaemin (1 nM) induced a transient rise in intracellular free calcium. AR4–2J cells synthesize amylase, and exposure of cells to SP resulted in a dose-dependent increase in amylase secretion.(ABSTRACT TRUNCATED AT 250 WORDS)