Arginine infusion increases peripheral plasma somatostatin in man.
A somatostatin (SRIF) radioimmunoassay is described, using an antiserum raised in rabbit, reacting more with SRIF-14 than -28. Glass tubes were employed for the assay because our tracer, 125I 1-Tyr-SRIF, was adsorbed to plastic (23% non specific binding). Vycor extraction was used, and following Sephadex G-50 chromatography, the plasma extract showed two forms, coeluting with SRIF-28 and -14. Fifteen healthy subjects, eight women and seven men, 21-39 years old, received an infusion of arginine chloride (2.38 mmol/kg) for 20 min, or saline. An immediate rise in plasma SRIF from the mean basal level at 2 min was shown. Maximal value was 24.0 +/- 3.0 pmol/l (P less than 0.01) after 10 min followed by a rapid descent towards the basal level after the infusion. A temporal relationship was observed between the SRIF, insulin and glucagon responses following arginine infusion, while the GH levels increased only after the SRIF levels had declined, indicating an inhibition of GH. This is further supported by the high degree of correlation (r = 0.87) between SRIF- and GH increments. It is suggested that plasma SRIF measurement during arginine infusion gives an estimate of the pancreatic SRIF releasing capacity.