This Article Full Text (PDF) Submit a related Letter to the Editor Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Copyright Permission Citing Articles Citing Articles via Google Scholar Google Scholar Articles by RABBANI, S. N. Articles by PATEL, Y. C. Search for Related Content PubMed PubMed Citation Articles by RABBANI, S. N. Articles by PATEL, Y. C.

Measurement and Characterization of Somatostatin-14-Like Immunoreactivity in Human Urine^*

SHAHIDA N. RABBANI and YOGESH C. PATEL

Fraser Laboratories Montreal, Quebec, Canada
McGill University Montreal, Quebec, Canada
The Departments of Medicine and Neurology and Neurosurgery, Royal Victoria Hospital Montreal, Quebec, Canada
The Montreal Neurological Institute Montreal, Quebec, Canada

Address all correspondence and requests for reprints to: Dr. Y. C. Patel, Room M3-15, Royal Victoria Hospital, 687 Pine Avenue West, Montreal, Quebec, H3A 1A1 Canada.

Timed urine collections were obtained from normal men and women for a study of somatostatin in urine. Somatostatin-14-like immunoreactivity (S-14 LI) was extracted from urine by adsorption to C-18 silica cartridges, and the extracts were analyzed by RIA directly or after gel and high pressure liquid chromatography (HPLC). S-14 LI was consistently detected in all urine samples. The mean S-14 LI content in 24-h collections in men [10.96 ± 0.91 (±SE) pmol/24 h; n = 10; total volume, 1.96 ± 0.09 L] was not significantly different from that in women (9.09 ± 0.85 pmol/24 h; n = 10; total volume, 1.87 ± 0.09 L). Gel chromatography of 24-h urine collections revealed three major peaks of S-14 LI coeluting with S-14, S-28, and a 12,000 mol wt species corresponding to prosomatostatin. HPLC analysis confirmed the presence of S-14, S-28, and the 12,000 mol wt form and additionally revealed a major fourth peak of 3,000 mol wt, closely related to S-28. Immunoreactivity corresponding to [Des,Ala¹]S-14 (S-13) was identified by HPLC coelution with synthetic S-13 and reactivity in a centrally, but not N-terminally directed, S-14 RIA. The relative proportions of the different HPLC peaks varied considerably during the 24-h period. S-14 and S-28 were excreted preferentially during the day, whereas the 12,000 and 3,000 mol wt forms were excreted preferentially at night. The ingestion of a mixed meal evoked parallel increases in plasma S-14 LI and urinary S-14 LI excretion in six normal subjects. We conclude that the principal circulating forms of S-14 LI (S-14, S-28, S-13, and pro-S) are present in urine and that the measurement of urinary S-14 LI could provide a reliable index of integrated plasma S-14 LI concentrations.

^* Presented at the International Somatostatin Symposium, Washington, D. C, May 1986, and the Annual Meeting of the Canadian Society For Clinical Investigation, Toronto, Ontario, Canada, September 1986. This work was supported by grants from the Canadian Medical Research Council (MT-6196) and the NIH (AM-21373).

Scientist of the Canadian MRC.

Received September 10, 1987.