Effect of antrectomy and drug-induced achlorhydria on urinary excretion of N-terminal big gastrin immunoreactivity in rats.

Immunoreactivities of urinary N-terminal big gastrin and serum C-terminal gastrin were determined in intact and antrectomized rats by radioimmunoassay using two antisera specific for N- and C-termini of big gastrin, respectively. Gel filtration of urine extract from intact rat showed a single giant peak of N-terminal big gastrin immunoreactivity eluted in a later position than 1-17 gastrin-34, indicating that N-terminal peptides smaller than 1-17 gastrin-34 are excreted in urine. Serum C-terminal gastrin concentration in antrectomized rats was about one sixth that in intact rats. Urinary excretion of N-terminal big gastrin in antrectomized rats was about one sixth that in intact rats. 2 week treatment with E3810, a proton pump inhibitor, (40 mg/kg/day, s.c.) induced urinary excretion of N-terminal big gastrin in parallel with a marked increase in serum C-terminal gastrin concentration in intact rats. Antrectomy completely prevented both the increase in urinary excretion of N-terminal big gastrin and the elevation of serum C-terminal gastrin induced by administration of E3810. There was an excellent correlation between serum concentration of C-terminal gastrin and urinary excretion of N-terminal big gastrin. These results suggest that urinary N-terminal big gastrin, which mostly originates from the gastric antrum, is a useful indicator of gastrin secretion in the rat.