Ultrastructures of G cells and the mechanism of gastrin release before and after selective vagotomy with pyloroplasty.

A combined, electron microscope 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.1. After SV+P, G cells did not show any degenerative or hypofunctional signs in their fine structure, but their secretory granules trended towards the cell base, suggesting 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 better prognosis, blood gastrin levels dropped more or less conspiciously as the main source of G cells had been removed.2. G cells denervated by surgery (SV+P), reacted to the stimuli of meat extract by releasing their granules and elevating blood gastrin levels, as the innervated G cells do. The response of G cells to the luminal stimuli is thus not believed to be essentially related to nerves.3. The denervated G cells also could, as innervated ones, release gastrin in response to insulin hypoglycemia. Thus it is proposed that this stimulation is not mediated by the vagal nerve.4. Gastrin release from the G cell was evidenced in this study as emiocytotic granule release from the cell base. The frequency of the Ω-shaped granule openings found in the electron microscope well corresponded to the gastrin levels in the blood.