L-Type calcium channels in enterochromaffin cells from guinea pig and human duodenal crypts: an in situ study.
OBJECTIVE
This study has investigated stimulus-secretion coupling of enterochromaffin cells by studying the cellular location and function of voltage-gated Ca(2+) channels within small intestinal crypts.


METHODS
Digital fluorescence imaging and electrochemical detection were used to measure intracellular Ca(2+) responses and serotonin (5-hydroxytryptamine [5-HT]) secretion in intact crypts isolated from guinea pig and human duodenum.


RESULTS
In fluo-3-loaded crypts, electrical depolarization with high K(+) solution increased cytosolic free [Ca(2+)] only in single cells subsequently identified by immunocytochemistry as enterochromaffin cells. In guinea pig enterochromaffin cells, the L-type Ca(2+) channel agonist FPL 64176 (3 micromol/L) did not change resting intracellular [Ca(2+)] but potentiated the depolarization-evoked increase in [Ca(2+)] (298 +/- 72 nmol/L) by 19 +/- 3-fold. In the majority of human enterochromaffin cells, FPL 64176 alone increased resting [Ca(2+)] by 423 +/- 171 nmol/L. Secretion studies in guinea pig crypts showed that high K(+) and FPL 64176 caused a 12-fold increase in 5-HT release. Noradrenaline caused increases in both enterochromaffin cell [Ca(2+)] and 5-HT release.


CONCLUSIONS
Using this approach, we have found that in duodenal crypts, enterochromaffin cells, but not other epithelial cells, contain L-type voltage-gated Ca(2+) channels involved in regulating 5-HT secretion. These data have implications for the pharmacological control of intestinal disorders involving enterochromaffin cell dysfunction.
Lomax
R B
RB
Section of Gastrointestinal Science, Clinical Division I, University of Manchester, Salford, England.
Gallego
S
S
Novalbos
J
J
García
A G
AG
Warhurst
G
G
D000814:Aniline Compounds / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020746:Calcium Channels, L-Type / Q000032:analysis / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D004386:Duodenum / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D004759:Enterochromaffin Cells / Q000187:drug effects / Q000378:metabolism*; D006168:Guinea Pigs; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D008297:Male; D012701:Serotonin / Q000378:metabolism; D014966:Xanthenes / Q000378:metabolism
D000814:Aniline Compounds; D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D014966:Xanthenes; C059715:Fluo-3; D012701:Serotonin; D002118:Calcium