Regulation of Postjatal Intestinal Maturation by Growth Hormone: Studies in Rats with Isolated Growth Hormone Deficiency

Abstract

During the 3rd wk of postnatal life in the rat, dramatic maturational changes occur in the structure and function of the small intestine, enabling the animal to make the transition from milk to solid food. To investigate the role of GH in the regulation of this complex process, we studied postnatal intestinal maturation in the spontaneous dwarf rat, a strain of Sprague-Dawley rats with an autosomal recessive mutation in the GH gene resulting in complete but isolated GH deficiency. GH-deficient and GH-normal littermates were studied at d 7 and 14 (suckling) and d 23 (postweaned). The body weight of GH-deficient animals was inhibited by 60% at each age. Longitudinal growth of the small intestine was not inhibited, suggesting that longitudinal small bowel growth is independent of GH regulation. Mucosal cell mass was significantly lower in GH deficiency at all ages studied, and digestive hydrolase capacity per cm of intestine was significantly lower in GH-deficient postweaned animals. However, epithelial cell mass increased markedly in association with weaning and the maturation of lactase, sucrase, and aminooligopeptidase proceeded normally in GH deficiency. These data suggest that, although GH is not required for normal postnatal intestinal maturation, the mucosal epithelial hypoplasia found in GH-deficient animals suggests that GH or GH-dependent factors act as an intestinal mucosal growth factor whose function is to promote the homeostatic or steady-state regulation of mucosal epithelial growth.

Effect of Age and Weaning on Gastric Mucosal Injury in Developing Rats

“…The mechanism that regulates or influences the maturational changes in mucosal protection is not known [11,[17][18][19]. We hypothesized that the dietary change from maternal milk to rat chow has some role in maturation.…”

Development of gastrointestinal and pancreatic functions in mammalians (mainly bovine and porcine species): influence of age and ingested food

“…The levels of mRNA specific for amylase, lipase and trypsin increase 10-, 8 [91]. Growth hormone is not required for normal postnatal maturation of the small intestine, although it acts by promoting homeostasis or steady-state regulation of mucosal epithelial growth [21]. Somatostatin and luteinizing releasing hormone (Lh-RH) inhibit the proliferation of gastric epithelium cells in rats [27].…”

Alterations of growth hormone, cortisol, luteinizing hormone, and insulin concentrations in early-postnatal calves affected with diarrhea

“…This is comparable to the findings of Ronge and Blum [13] who described that in new-born calves GH concentrations tended to decrease during the first five weeks of life. The high concentrations of GH may have a comparable action a) on the increase in the depth of crypts and b) on the rate of proliferation of the villi of the gut [14]. In this study GH concentrations were elevated before symptoms of diarrhea could be observed.…”