Gastrin processing and secretion in patients with end-stage renal failure.

Abstract

Gastrin circulates at higher than normal concentrations in patients with end-stage renal failure (ESRF). However, it remains unclear which forms of gastrin are elevated and whether there is also an alteration in the secretory profile after stimulation. In the present study all processed and partially processed forms of circulating gastrin were measured in plasma before and after meal stimulation in ESRF patients and control subjects. Since Helicobacter pylori (HP) infection affects gastrin secretion, HP status was determined. Fasting gastrin-amide (36 +/- 8 pmol/L), gastrin-Gly (55 +/- 16 pmol/L), and total gastrin (218 +/- 32 pmol/L) measured in ESRF/HP-patients were all significantly greater than those in the control group (10 +/- 1, 15 +/- 3, and 17 +/- 2 pmol/L, respectively; P < 0.01). Plasma gastrin-amide (126 +/- 67 pmol/L) and total gastrin (397 +/- 164 pmol/L) were highest in the ESRF/HP+ patients. The proportion of nonamidated gastrin products was 4-fold higher in ESRF patients than in control subjects, suggesting structure-specific changes in gastrin secretion and metabolism, and this was confirmed by chromatography. The meal-stimulated increments in control/HP- and ESRF/HP-groups were similar. However, the ESRF/HP+ group had a markedly potentiated gastrin response. Fasting plasma somatostatin, an inhibitor of gastrin secretion, was also measured and was significantly lower in the ESRF patients than that in the control group. These studies show that the hypergastrinemia associated with renal failure has been underestimated. This is because only amidated products were measured. The potentiated gastrin meal response in ESRF attributed previously to changes in gastrin metabolism are in part explained by the effect of HP infection. The observed diminished somatostatin response suggests that the increase in circulating gastrin in ESRF is the result of loss of inhibition of secretion as well as decreased metabolism. As both amidated and nonamidated gastrin are now considered to have trophic and secretory effects, these findings may explain the gastrointestinal tract hypertrophy often associated with ESRF.