Abstract
Isolated circular smooth muscle cells from the esophagus, fundus, and antrum in the adult cat and newborn kitten were compared. Dose response curves were obtained to Acetylcholine (Ach) in the presence of normal Calcium (Ca+2), zero Ca+2, and the Ca+2 channel blocker D600. Cells from the esophagus of the adult and kitten contracted similarly in Ca+2, but both failed to show any contraction in zero Ca+2 or D600. Fundic cells in both the adult and kitten contracted the same in Ca+2, and also showed maximal contraction in zero Ca+2 or D600. The contractile response of antral cells was no different between adult and kitten in normal Ca+2. However, the adult antrum contracted 53.3% and 47.6% of maximum in zero Ca+2 and D600 respectively, while the kitten's antrum contracted significantly less (p< .001) at 6.4% and 3.2% of maximum. Antral cells were then saponified (permeabilized) and exposed to inositol tri-phosphate (IP3), which releases intra-cellular Ca+2 stores. With IP3 adult antral cells contracted 52.1%, while the kitten antral cells failed to contract. We conclude that in response to Ach the esophagus and fundus of the adult cat and kitten utilize similar Ca+2 sources, with the esophagus using extracellular Ca+2 and the fundus depending upon intracellular Ca+2 stores. The adult antrum is able to utilize intracellular Ca+2 stores for part of it's contraction while the kitten is not. We speculate this may be due to a lack of intracellular Ca+2 stores in the newborn kitten antrum.
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Hillemeier, C., Bereiter, D. & Biancani, P. DEVELOPMENTAL DIFFERENCES IN CALCIUM SOURCES UTILIZED FOR CONTRACTION IN THE CAT'S UPPER GASTROINTESTINAL TRACT. Pediatr Res 21 (Suppl 4), 269 (1987). https://doi.org/10.1203/00006450-198704010-00614
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DOI: https://doi.org/10.1203/00006450-198704010-00614