Ultrastructures of G Cells and the Mechanism of Gastrin Release before and after Selective Vagotomy with Pyloroplasty

Abstract

A combined, EM and radioimmunoassay investigation was carried out on the G cells and blood gastrin levels in patients who received either selective vagotomy (SV) plus pyloroplasty (P) or selective vagotomy plus antrectomy (A) for duodenal ulcer. After SV + P, G cells did not show any degenerative or hypofunctional signs in their fine structure, but their secretory granules suggested a presecretory state. Six months postoperatively, the G cells were markedly increased in number (hyperplasia). In accordance, basal gastrin levels were elevated (hypergastrinemia). After SV .+-. A, which caused a better prognosis, blood gastrin levels dropped more or less conspiciously as the main source of G cells had been removed. G cells denervated by surgery (SV + P) reacted to the stimuli of meat extract by releasing their granules and increasing blood gastrin levels, like the innervated G cells do. The response of G cells to the luminal stimuli is not believed to be essentially related to nerves. The denervated G cells also could, like the innervated ones, release gastrin in response to insulin hypoglycemia. This stimulation probably is not mediated by the vagal nerve. Gastrin release from the G cell was evident as emiocytotix granule release from the cell base. The frequency of the .OMEGA.-shaped granule openings found in the EM corresponded well to the gastrin levels in the blood.