Secretion of Gastrointestinal Hormones

Abstract

Compared with development in other fields of hormone research, one must describe advances in the knowledge of gastrointestinal hormones as stumbling. The first evidence suggesting the existence of hormones in the mu cosa of the gastrointestinal tract was provided by Bayliss & Starling-for se cretin in 1902 (13), and by Edkins-for gastrin in 1905 (25). Apart from occasional important discoveries, gastrointestinal hormone research was then more or less dormant for almost 50 years. During this time there was much controversy as to whether the postulated hormones really existed; in fact, this debate continued until the hormones had been chemically identified and their specific biological actions subsequently demonstrated.As a result of the participation of research workers from several different branches of medical science, a considerable amount of new information on gastrointestinal hormones has accumulated during the last ten years, and this has acted as a strong stimulus to further research in this area. Morphologists have provided evidence on particular cells in the mucosa of the gastrointesti nal tract that might harbor various hormonal substances. Biochemists have succeeded in identifying, determining the structures of, and synthesizing the three "old" hormones, gastrin, secretin, and cholecystokinin-pancreozymin. Access to pure hormonal substances has made it possible for immunologists to work out sensitive and specific radioimmunoassays whereby the hormones can be detected and measured in tissues and body fluids. WHAT ARE THE CRITERIA FOR A GASTROINTESTINAL HORMONE?In recent years the number of possible candidates for new hormones has increased considerably. Evidence for a new gastrointestinal hormone has been based either on purely physiological observations or on the chemical isolation of a new agent from the gastrointestinal tract. It is therefore particu larly important for the following discussion to decide criteria that must be fulfilled before an agent can be classified as a gastrointestinal hormone. By definition, a hormone is a discrete chemical substance secreted by a specific tissue and transported to a distant site where it exerts its effect upon other specific tissues. Thus, in order to prove the existence of a gastrointestinal hor mone by physiological means one must show that the application of a physio-431 Annu. Rev. Physiol. 1973.35:431-452. Downloaded from www.annualreviews.org Access provided by Michigan State University Library on 02/03/15. For personal use only.Quick links to online content Further ANNUAL REVIEWS