Somatostatin 1-28 circulates in human plasma

Area of Science:

• Endocrinology
• Biochemistry
• Analytical Chemistry

Background:

• The precise characterization of circulating somatostatin in human plasma is limited due to the low sensitivity of conventional chromatography and radioimmunoassay techniques.
• Previous studies lacked the sensitivity to reliably establish the gel filtration profile of immunoreactive somatostatin in fasting human plasma.

Purpose of the Study:

• To establish the gel filtration profile of immunoreactive somatostatin in human plasma.
• To identify and quantify circulating somatostatin components in plasma using a more sensitive method.

Main Methods:

• Plasma samples were concentrated using batchwise immunoaffinity chromatography.
• Gel permeation chromatography was employed to analyze the concentrated plasma samples.
• Radioimmunoassay was used to detect somatostatin-like immunoreactivity.

Main Results:

• The study successfully documented the gel filtration profile of immunoreactive somatostatin in human plasma.
• A circulating peptide with a gel permeation chromatography profile identical to synthetic somatostatin 1-28 was identified.
• Approximately 46% of the total somatostatin-like immunoreactivity in plasma was attributed to this identified peptide component.

Conclusions:

• The enhanced sensitivity achieved through immunoaffinity concentration reliably identified a circulating somatostatin peptide in human plasma.
• The primary circulating form of somatostatin in human plasma is identical to synthetic somatostatin 1-28.
• This finding clarifies the composition of circulating somatostatin and its contribution to total plasma immunoreactivity.