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A somatostatin receptor 1 selective ligand inhibits Ca2+ currents in rat insulinoma 1046-38 cells
D Roosterman1, G Glassmeier, H Baumeister
1Abteilung Molekulare Genetik, Deutsches Institut für Ernährungsforschung, Potsdam-Rehbrücke, Germany.
Abstract:
Rat insulinoma 1046-38 cells represent a model system to study beta-cell function. The mRNAs for sst1 and sst2, two of the five somatostatin receptors, were detected by reverse transcription polymerase chain reaction amplification in these cells. Displacement binding analysis suggested that sstl represents the major somatostatin receptor subtype. The sstl selective compound CH-275 did not inhibit adenylyl cyclases while compounds that activated sst2 did. In contrast, CH-275 caused a marked inhibition of voltage-operated Ca2+ channels while the sst2 specific analog octreotide elicited a less pronounced effect suggesting that in rat insulinoma 1046-38 cells sst1 preferably mediates the inhibition of Ca2+ channels.
Insights
In rat insulinoma cells, somatostatin receptor 1 (sst1) primarily inhibits calcium channels, while somatostatin receptor 2 (sst2) affects adenylyl cyclase activity, revealing distinct functional roles.
Area of Science:
- Endocrinology
- Molecular Biology
- Cell Physiology
Background:
- Rat insulinoma 1046-38 cells are a key model for studying pancreatic beta-cell function.
- Five somatostatin receptors (SSTRs) exist, with subtypes sst1 and sst2 being investigated in this study.
- Understanding SSTR function is crucial for metabolic disease research.
Purpose of the Study:
- To investigate the specific roles of somatostatin receptor 1 (sst1) and somatostatin receptor 2 (sst2) in rat insulinoma 1046-38 cells.
- To determine the signaling pathways preferentially activated by sst1 and sst2.
- To elucidate the contribution of each receptor subtype to cellular functions like calcium channel modulation.
Main Methods:
- Detection of sst1 and sst2 mRNA using reverse transcription polymerase chain reaction (RT-PCR).
- Displacement binding analysis to identify the predominant somatostatin receptor subtype.
- Functional assays using subtype-selective ligands (CH-275 for sst1, octreotide for sst2) to assess adenylyl cyclase and voltage-operated calcium channel activity.
Main Results:
- Both sst1 and sst2 mRNAs were detected in rat insulinoma 1046-38 cells.
- Displacement binding indicated sst1 as the major somatostatin receptor subtype present.
- The sst1-selective compound CH-275 inhibited voltage-operated Ca2+ channels but not adenylyl cyclase.
- sst2-activating compounds inhibited adenylyl cyclase, and octreotide showed a less pronounced effect on Ca2+ channels compared to CH-275.
Conclusions:
- In rat insulinoma 1046-38 cells, sst1 preferentially mediates the inhibition of voltage-operated calcium channels.
- sst2 activation is associated with adenylyl cyclase inhibition.
- These findings highlight distinct functional pathways for sst1 and sst2 in beta-cells, impacting cellular signaling and function.