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Updated: Aug 12, 2026

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Published on: April 24, 2012

Mechanisms of somatostatin action in RINm5F cells in culture: preliminary evidence for possible altered G protein

M K McLeod1, P Kothary, M Warnock

  • 1Department of Surgery, University of Michigan Medical Center, Ann Arbor 48109-0331.

The Journal of Surgical Research
|November 1, 1992
PubMed

Insights

Octreotide (SMS) does not inhibit insulinoma cell growth, but it significantly reduces insulin secretion and cAMP levels. Pretreatment with pertussis toxin (PT) enables SMS to inhibit DNA synthesis in these cells.

Area of Science:

  • Endocrinology
  • Molecular Biology
  • Cancer Research

Background:

  • Octreotide (SMS), a somatostatin analogue, is known for its anti-growth properties but shows limited efficacy against insulinoma cell proliferation.
  • Understanding the mechanisms behind SMS's limited antiproliferative effect on insulinoma cells is crucial for developing targeted therapies.

Purpose of the Study:

  • To investigate the mechanisms underlying the lack of antiproliferative effect of Octreotide (SMS) on rat insulinoma cell line (RINm5F).
  • To evaluate the impact of SMS on DNA synthesis, insulin secretion, and intracellular cAMP levels in RINm5F cells.

Main Methods:

  • Establishment and culture of the rat insulinoma cell line, RINm5F.
  • Measurement of [3H]-thymidine incorporation into DNA (TTID) to assess proliferation.
  • Quantification of insulin (IRI) and intracellular cAMP (cAMPi) using radioimmunoassay (RIA).
  • Assessment of cell viability using trypan blue exclusion tests.

Main Results:

  • Octreotide (SMS) did not significantly affect TTID in RINm5F cells with 1% FBS.
  • SMS significantly decreased insulin secretion and intracellular cAMP levels in a dose-dependent manner.
  • A significant inhibition of TTID by SMS was observed after a 4-hour pretreatment with pertussis toxin (PT).

Conclusions:

  • The inhibition of insulin secretion by SMS is linked to the attenuation of cAMP formation.
  • Pertussis toxin (PT) pretreatment unmasks the antiproliferative effect of SMS on insulinoma cells, suggesting a role for G-protein signaling pathways.

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