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Possible modulatory role of non-activated lymphocytes on insulin secretion
A F Meira1, P M Freire, M S Rocha
1Departamento de Fisiologia e Biofísica, Universidade de São Paulo, Brasil.
Insights
Non-activated lymphocytes directly impact islet B-cells, reducing insulin secretion and altering ion fluxes. This suggests lymphocytes play a physiological role in regulating pancreatic islet function.
Area of Science:
- Immunology
- Endocrinology
- Cell Biology
Background:
- The physiological role of non-activated lymphocytes on pancreatic islet B-cells remains unclear.
- Understanding lymphocyte-islet interactions is crucial for comprehending glucose homeostasis and potential autoimmune mechanisms.
Purpose of the Study:
- To investigate the direct physiological effects of non-activated lymphocytes on rat pancreatic islet B-cells.
- To determine if lymphocyte contact or secreted substances mediate changes in insulin secretion and ion fluxes.
Main Methods:
- Rat pancreatic islets were incubated and perfused under low (2.8 mM) and high (16.7 mM) glucose conditions.
- Islets were pre-exposed to either rat lymphocytes or substances secreted by lymphocytes for 60 minutes.
- Insulin secretion, potassium-45 (45Ca2+), rubidium-86 (86Rb+), and phosphoinositide metabolite fluxes were measured.
Main Results:
- Pre-exposure to lymphocytes significantly reduced insulin secretion and isotope fluxes compared to controls.
- Exposure to lymphocyte-secreted substances alone did not alter insulin secretion or isotope fluxes.
- Lymphocyte contact induced potassium channel closure and altered insulin release under low glucose conditions.
Conclusions:
- Direct contact between non-activated lymphocytes and islet B-cells significantly impairs insulin secretion and ion transport.
- These effects are likely mediated by a rapid, direct action of lymphocytes on islet cells, possibly involving secreted factors.
- Lymphocytes may play a direct physiological role in modulating pancreatic islet function.
Abstract:
In order to study the probable physiological role of non-activated lymphocytes on islet B-cells, we incubated and perfused rat pancreatic islets in the presence of low (2.8 mM) and high (16.7 mM) glucose concentrations after pre-exposure for 60 min to rat lymphocytes or to substances secreted by lymphocytes. Insulin secretion and 86Rb+, 45Ca2+ and [3H]-phosphoinositide metabolite fluxes were lower compared to controls when islets were pre-exposed to lymphocytes but were not different when islets were pre-exposed to substances secreted by lymphocytes. These alterations in isotope flux suggest that, when lymphocytes and islets are in contact, closure of potassium channels and a paradoxical effect of glucose load on insulin release occur in the presence of low glucose concentrations. The alterations observed are probably due to a swift and direct action of lymphocyte secretion perhaps induced by a direct of islet cells.