5-HT induces cAMP production in crypt colonocytes at a 5-HT4 receptor

• Published in: The Journal of surgical research 1998-07, Vol.77 (2), p.137-140
• Main Authors: ALBUQUERQUE, F. C, SMITH, E. H, KELLUM, J. M
• Format: Article
• Language: English
• Subjects: Adenylyl Cyclases - metabolism; Animals; Biological and medical sciences; Chlorides - metabolism; Colon - chemistry; Colon - cytology; Colon - metabolism; Cyclic AMP - biosynthesis; Dose-Response Relationship, Drug; Gastroenterology. Liver. Pancreas. Abdomen; Indoles - pharmacology; Intestinal Mucosa - chemistry; Intestinal Mucosa - enzymology; Keratins - analysis; Ketanserin - pharmacology; Male; Medical sciences; Ondansetron - pharmacology; Other diseases. Semiology; Rats; Rats, Sprague-Dawley; Receptors, Serotonin - metabolism; Receptors, Serotonin, 5-HT4; Serotonin - pharmacology; Serotonin Antagonists - pharmacology; Staining and Labeling; Stomach. Duodenum. Small intestine. Colon. Rectum. Anus; Sulfonamides - pharmacology; Thymidine - pharmacology; Tritium
• ISSN: 0022-4804; 1095-8673
• DOI: 10.1006/jsre.1998.5361

Previous studies demonstrate that both 5-hydroxytryptamine (5-HT) and cyclic AMP (cAMP) induce chloride efflux from crypt colonocytes in the rat distal colon; antagonist studies suggest that the 5-HT response is mediated primarily by the 5-HT4 receptor. Since this receptor is known to be positively coupled to adenylate cyclase, we postulated that 5-HT should induce generation of cAMP, which should be inhibited by 5-HT4 antagonists. Method. Mucosal cells from rat distal colon were taken by a sequential calcium chelation technique for enrichment of crypt cells. Cytokeratin stains demonstrated that >99% of cells were colonocytes. [3H]Thymidine uptake studies demonstrate a fivefold increased incorporation in this cell preparation compared to earlier fractions. 3-Isobutyl-l-methylxanthine (IBMX, 100 microM) was added to all cell suspensions in order to prevent cAMP metabolism. Cell suspensions were incubated for 2 min at 37 degreesC with different concentrations of 5-HT (n = 7). cAMP was measured by enzyme immunoassay. In another series of experiments, 5-HT (0.3 microM) stimulation of cAMP was similarly measured in the presence and absence of 5-HT receptor antagonists: 10 microM 5-HTP-DP (5-HT1P; n = 4), 0.1 microM ketanserin (5-HT2A; n = 4), 0.3 microM ondansetron (5-HT3; n = 4), 3 microM tropisetron (5-HT3 and 5-HT4; n = 4), and 10 nM GR-113808 (5-HT4; n = 5). Results. 5-HT produced a dose-dependent increase in cAMP. The increase was significant at concentrations >/=0.3 microM when compared to cells incubated with IBMX alone. In the second series of experiment, 5-HT-induced generation of cAMP at a dose of 0.3 microM was significantly inhibited in the presence of GR-113808 and tropisetron. Conclusion. 5-HT acts at a 5-HT4 receptor to induce production of cAMP in rat distal crypt colonocytes.