( Gastrin ( ( is ( responsible ( for ( ( ( action ( on ( the ( ECL cells ) ) ) ) , ) ( which ( release ( ( histamine , ) ( ( the ( ( most important ) stimulant ) ) ( of ( gastric ( acid secretion ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Gastrin)) (VP (VBZ is) (ADJP (JJ responsible) (PP (IN for) (NP (NP (NN action)) (PP (IN on) (NP (DT the) (NNP ECL) (NNS cells))) (, ,) (SBAR (WHNP (WDT which)) (S (VP (VBP release) (NP (NP (NN histamine)) (, ,) (NP (NP (DT the) (ADJP (RBS most) (JJ important)) (NN stimulant)) (PP (IN of) (NP (JJ gastric) (JJ acid) (NN secretion)))))))))))) (. .)))
Gastrin is responsible for action on the ECL cells, which release histamine, the most important stimulant of gastric acid secretion.
(ROOT (S (NP (NNP Gastrin)) (VP (VBZ signals) (NP (NP (DT the) (NN secretion)) (PP (IN of) (NP (JJ gastric) (NN acid))))) (. .)))