19 Regulation of Cell Growth in the Endocrine Pancreas

Abstract

Organs of metazoans are subject to two distinct challenges in terms of growth. First, they have to maintain appropriate size during development, only achieving at maturity a final mass commensurate with the size and requirements of the organism. There is a second need for growth in both the adult and developing organism. To meet specific physiological responsibilities, many organs exhibit compensatory growth. For example, following partial hepatectomy, the liver has the ability to regenerate itself. On the other hand, the kidney, after unilateral nephrectomy, compensates by hypertrophy of the remaining organ. Several endocrine organs, including adrenal, parathyroid, and thyroid, show compensatory growth by both hyperplasia (an increase in cell number) and hypertrophy (an increase in cell volume). In this chapter, we discuss the contribution of islet/β-cell growth to the change in endocrine pancreatic mass that accompanies normal development or compensation for an increased requirement for insulin. In addition, we examine the role of the insulin/insulin-like growth factor (IGF) signaling pathway in the determination of β-cell growth and proliferation.

A few comments are required before we discuss β-cell growth in more detail. First, only recently have investigators become conscious of independent regulation of growth and proliferation, and therefore, studies in which these parameters are carefully examined are few. Second, considerable attention has been given to the concept of β-cell mass as an indication of fundamental functional capacity. As is true for most tissues, mass has generally been regarded as determined by the rate of proliferation of β-cells minus the rate of...