Background and Aims: Unlike adult antral cells, feline newborn antral cells are unable to contract in response to agonists in the absence of extracellular calcium or in response to exogenous inositol 1,4,5-triphosphate (IP3) after permeabilization. Changes in intracellular pathways that are associated with these differences were examined. Methods: In adult and kitten antrum isolated smooth muscle cell contraction, levels of 1,2-diacylglycerol (DAG) and IP3 were assessed in response to cholecystekinin (CCK). Results: CCK-induced contraction was transient in the adult and sustained in the kitten. U73122 blocked contraction in adult antral cells but not kitten antral cells. In adult antral tissue, CCK (3.0-7 mol/L) caused an early transient increase in the level of DAG, whereas in the newborn antrum, CCK (10-7 mol/L) caused a sustained increase in the DAG level for up to 4 minutes. IP3 showed an early increase in both age groups. Newborn contraction is associated with an initial increase in IP3 and sustained elevation of DAG levels, whereas in adult antral cells, there is a transient increase in both IP3 and DAG. Conclusions: The relative inaccessibility of intracellular calcium stores in the newborn is associated with age-related differences in signal transduction pathways.
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