LEUKOTRIENE-B(4) AND C(4) PRODUCTION IN ISOLATED RAT GASTRIC-MUCOSAL CELLS

Dispersed rat gastric mucosal cells (F0) were separated into five frac tions (F1-F5) by counterflow elutriation, with F1 representing the sma llest and F5 the largest cell diameters. In F0-F5, leukotriene B4 (LTB 4) release in response to 10(-5) M calcium ionophore A-23187 was 7.68 +/- 1.26, 51.6 +/- 10.8, 72.4 +/- 10.4, 7.1 +/- 0.7, 5.7 +/- 0.6, and 11.6 +/- 3.4 pg . 10(6) cells-1 . 30 min-1. In the identical fractions , sulfidopeptide release in response to A-23187 was 200.6 +/- 20.5, 1, 116.0 +/- 166.6, 1,309.4 +/- 163.2, 189.8 +/- 25.8, 108.0 +/- 18.0, an d 158.4 +/- 54.0 pg . 10(6) cells-1 . 30 min-1. High-pressure liquid c hromatography verified the radioimmunologically determined LTB4 and id entified LTC4 as the only sulfidopeptide LT released. LT release from F2 cells in response to A-23187 was time and dose dependent, reaching maximal stimulation at 10(-5) M A-23187. This response was blocked by the dual inhibitor of cyclooxygenase and lipoxygenase, BW755C (2 x 10( -5)-2 x 10(-4) M), by the selective 5-lipoxygenase inhibitor L-651,392 (10(-7)-10(-5) M), and by MK-886 (10(-9)-10(-7) M), which blocks tran slocation of 5-lipoxygenase. The postreceptor stimuli dibutyryl adenos ine 3',5'-cyclic monophosphate, forskolin, 12-O-tetradecanoylphorbol-1 3-acetate, and oleyl-acetyl-glycerol failed to induce LT release. Howe ver, 10(-4) M arachidonic acid increased basal LT release up to eightf old and increased A-23187-stimulated LT release by an additional 30%. There was no stimulation of LT release in response to platelet-activat ing factor, interleukin-1 and -2, N-formyl-Met-Leu-Phe, histamine, or pentagastrin. LT release did not-correlate with the distribution of gr anulocytes, macrophages, mast cells, D-cells, or G-cells. However, cor responding to the peak of LT release, chromogranin A-positive cells co ntributed 38 and 29% to the total cell number of F1 and F2, whereas F3 -F5 contained only 4-9% chromogranin A-positive cells. We conclude tha t LTs are produced by small cells of the rat gastric mucosa; the exact cell type(s) remain to be identified. Chromogranin A-positive neuroen docrine cells or an as yet unidentified cell type might represent a ma jor source of LT release. Calcium influx and 5-lipoxygenase activity a re the crucial regulatory mechanisms of LT production.