Regulation of the mucosal gastrin receptor.

The gastrin receptor in rat oxyntic gland mucosa is highly regulated. This regulation has so far only been found to be directed at the total numbers of receptors present. The affinity of the receptor is not altered significantly by agents which affect receptor numbers. Homospecific regulation occurs in that gastrin upregulates its receptor over long periods of time. Upregulation, however, appears to be preceded by a brief period of downregulation. During development corticosterone triggers the synthesis, or at least the appearance of gastrin receptors. Receptor development is maintained by solid food and presumably the gastrin it releases, but the change in diet which occurs at weaning does not in itself induce development. In female rats, estrogens prevent the increase of gastrin receptor levels to those found in males. These results with the gastrin receptor emphasize the importance of studying receptor concentrations as well as hormone levels to the total understanding of an endocrine response. They also suggest that the receptors of the other gastrointestinal hormones are likely to be regulated and that this regulation will probably be important in understanding some of the diseases of the gastrointestinal tract.