Calcitonin gene-related peptide receptors in human gastrointestinal epithelia.
1. The secretory responses to calcitonin gene-related peptide (CGRP) receptor agonists have been characterized in two human adenocarcinoma cell lines, namely HCA-7 and Colony-29 (Col-29) epithelia. These cells form polarized epithelial layers when grown on permeable supports and allow changes in electrogenic ion transport in response to agonists to be monitored continuously. 2. alpha-CGRP (rat and human sequences), rat beta-CGRP and human [Tyr0]CGRP applied to the basolateral surface were found to be full agonists, causing prolonged increases in short-circuit current. Concentration-response curves exhibited EC50 values of 0.6-1.5 nM in HCA-7 cells. The same agonists were less effective in Col-29 epithelia, the EC50 values ranging from 1 to 10 nM in these cells. [Cys(ACM)2,7]CGRP was effective in both cell lines and was more potent in HCA-7 cells. 3. CGRP receptors were preferentially located on the basolateral surface in both cell types. Addition of r alpha-CGRP to the apical domain produced significantly smaller secretory responses (8.1% in HCA-7 and 29.2% in Col-29) compared with those produced following basolateral application (100%). 4. In both cell lines r alpha-CGRP-elevated short-circuit current was inhibited by the loop diuretic piretanide (200 microM) and by somatostatin (100 nM). Pretreating epithelia with the cyclo-oxygenase inhibitor, piroxicam (5 microM) had no significant effect upon CGRP responses in either cell line. 5. Rat alpha-CGRP (0.2 nM) responses in HCA-7 epithelia were inhibited by the C-terminal fragment CGRP(8-37) (1 microM). Pretreatment of Col-29 cells with CGRP(8-37) did not, however, alter the size or profile of responses to r alpha-CGRP (1 nM).6. We conclude that high-affinity CGRP receptors exist on the basolateral surface of both cell lines,however they differ in their sensitivity to CGRP(8-37) and agonist orders of potency. Thus different CGRP receptor subtypes appear to predominate in these two epithelial cell types.
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Department of Pharmacology, Royal College of Surgeons of England, London.
Tough
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D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000031:analogs & derivatives / Q000494:pharmacology; D002460:Cell Line; D004232:Diuretics / Q000494:pharmacology; D004594:Electrophysiology; D004847:Epithelial Cells; D004848:Epithelium / Q000033:anatomy & histology / Q000378:metabolism; D005753:Gastric Mucosa / Q000033:anatomy & histology / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D007413:Intestinal Mucosa / Q000033:anatomy & histology / Q000187:drug effects / Q000378:metabolism*; D010894:Piroxicam / Q000494:pharmacology; D051381:Rats; D018015:Receptors, Calcitonin Gene-Related Peptide / Q000819:agonists / Q000378:metabolism*; D013004:Somatostatin / Q000494:pharmacology; D013449:Sulfonamides / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D004232:Diuretics; D018015:Receptors, Calcitonin Gene-Related Peptide; D013449:Sulfonamides; D010894:Piroxicam; D013004:Somatostatin; C015451:piretanide; D015740:Calcitonin Gene-Related Peptide