ONTOGENY OF INSULIN-LIKE GROWTH-FACTORS (IGF), IGF BINDING-PROTEINS, IGF RECEPTORS, AND GROWTH-HORMONE RECEPTOR MESSENGER-RNA LEVELS IN PORCINE PANCREAS

We examined the ontogeny of mRNA levels of IGF-I and -II, IGF type 1 ( IGFI-R) and type II receptors (IGFII-R), IGF binding protein-1 and -3 (IGFBP-1 and -3), GH receptor (GHR), and tissue concentrations of IGF and IGFBP in the pancreas of pigs. Tissues were collected from fetuses at 90 and 110 d of gestation and from pigs at 1, 21, 90 and 180 d of age. Northern blots were performed using total RNA hybridized with P-3 2-labeled cDNA probes (human IGF-I and human IGFI-R) and cRNA probes ( rat IGF-II, human IGFII-R, human IGFBP-1, pig IGFBP-3, and pig GHR). T here were two accelerated growth stages of the pancreas: the first one at 90 d of fetal life, which is characterized by cell hyperplasia (hi gh ratio of DNA to body weight), and the second one at postnatal 90 d, which is attributed to cell hypertrophy (high ratios of pancreatic we ight, RNA, and protein to DNA). The level of IGF-II mRNA and its tissu e concentration were predominant during fetal life and low thereafter. The IGF-I mRNA level was high during fetal and early postnatal life a nd decreased thereafter. Messenger RNA levels of IGFI-R, IGFBP-3, and GHR and concentrations of IGFBP-1 and -2 were abundant during fetal an d early postnatal life. In conclusion, IGF may be involved in various physiological periods of pancreatic development in pigs.