Binding of Epidermal Growth Factor to Receptors in Preparations of Enriched Porcine Parietal Cells and Inhibition of Aminopyrine Uptake

Abstract

Preparations of isolated porcine gastric cells, enriched in parietal cells, were used to study binding of epidermal growth factor (EGF) to receptors and subsequent inhibition of [¹⁴C]aminopyrine uptake. EGF in concentrations from 10⁻¹⁰ to 10⁻⁷M inhibited aminopyrine uptake stimulated by 10⁻⁵M histamine with an IC₅₀ of 3 . 10⁻¹⁰M. [¹²⁵]EGF bound in a saturable and specific manner to sites on cells in preparations containing 40-90% parietal cells. Mean apparent dissociation constant for the sites was 1.6 . 10⁻⁹M, with an average number of approximately 20,000 sites per cell. Endocytosis of ligand by parietal cells was limited, amounting to 10-20% of bound EGF after 1 h of incubation at 37° C. Occupation of a fraction of the receptors caused a maximal reduction by 40% of aminopyrine uptake in histamine-stimulated cells, suggesting the occurrence of spare receptors. The results indicate the existence of specific receptors for EGF on porcine parietal cells exerting a regulatory influence on acid secretion.

Key Words:

• [¹⁴C]Aminopyrine uptake
• epidermal growth factor
• histamine
• hog
• parietal cells
• receptors