Identification of a 5-hydroxytryptamine (5-HT2) receptor on guinea pig small intestinal crypt cells.
Radioligand labeling of [3H]ketanserin was examined in suspensions of dispersed guinea pig small intestinal mucosal cells prepared by modification of the EDTA-chelation method described by M. M. Weiser (J. Biol. Chem. 248: 2536-2541, 1973). Preferential incorporation of [3H]thymidine was used to confirm that suspensions were enriched in crypt cells. At 25 degrees C, binding of [3H]ketanserin to dispersed enterocytes was rapid, maximal by 5 min, saturable (dissociation constant = 1.5 nM), 65 +/- 5% specific, stable, and reversible. The maximal number of binding sites per cell was 92,000 (range 86,000-105,500). Binding was temperature dependent, with maximal binding at 37 degrees C, and was inhibited by 5-hydroxytryptamine (5-HT) (half-maximal inhibition of [3H]ketanserin binding observed in response to 1 microM 5-HT) and ketanserin (half-maximal inhibition of [3H]ketanserin binding observed in response to 1 nM ketanserin) but not by the 5-HT1P antagonist N-acetyl-5-hydroxytryptophyl 5-hydroxytryptophan amide (5-HTP-DP) or the 5-HT3 antagonist 3-tropanyl-indole-3-carboxylate methiodide (ICS-205-930). The second messenger system coupled to the putative mucosal 5-HT2 receptor was examined. 5-HT stimulated a concentration-dependent production of inositol 1,4,5-trisphosphate (IP3) in the dispersed enterocytes. This was maximal at 1 min and was inhibited in a concentration-dependent manner by ketanserin. 5-HTP-DP and ICS-205-930 had no effect on 5-HT-stimulated production of IP3. These data provide evidence for the existence of a mucosal 5-HT2 receptor located on guinea pig small intestinal crypt cells.
Siriwardena
A K
AK
Department of Surgery, Medical College of Virginia, Virginia Commonwealth University, Richmond 23298.
Smith
E H
EH
Borum
E H
EH
Kellum
J M
JM
D000818:Animals; D002469:Cell Separation; D002470:Cell Survival; D002478:Cells, Cultured; D002499:Centrifugation, Density Gradient; D006168:Guinea Pigs; D007295:Inositol Phosphates / Q000096:biosynthesis; D007413:Intestinal Mucosa / Q000166:cytology / Q000378:metabolism; D007421:Intestine, Small / Q000166:cytology / Q000378:metabolism*; D007650:Ketanserin / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000494:pharmacology; D008297:Male; D011985:Receptors, Serotonin / Q000378:metabolism*; D015290:Second Messenger Systems; D012701:Serotonin / Q000494:pharmacology; D013696:Temperature; D013997:Time Factors
D007295:Inositol Phosphates; D011985:Receptors, Serotonin; D012701:Serotonin; D007650:Ketanserin