HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Weller, P A Articles by Gilmour, R S Search for Related Content PubMed PubMed Citation Articles by Weller, P A Articles by Gilmour, R S

Genomic DNA encoding the 5' region of the porcine IGF-I gene was cloned and sequenced and shown to be highly homologous to that of man, rats and sheep. Two leader exons (exons 1 and 2), which are alternately spliced to exon 3 (encoding part of the mature IGF-I molecule), were identified by RNase protection analysis. In both cases, transcription initiates upstream from exons 1 and 2 at multiple dispersed start sites to yield two distinct IGF-I mRNA transcript classes (1 and 2) which differ in the precursor peptides predicted from their individual leader sequences.

The expression of class 1 and 2 transcripts was measured in liver and muscle RNA from two groups of 2-month-old pigs whose energy status had been manipulated within physiological limits to produce marked differences in plasma IGF-I levels and growth rates. For this purpose, RNase protection probes were developed that contained the individual leader exons 1 and 2 linked separately to the common exon 3, so that class-specific and total IGF-I gene expression could be determined in a single assay. At normal plasma IGF-I concentrations (200 ng/ml), class 1 and 2 transcripts comprised 81 and 19% respectively of total liver IGF-I mRNA, while at a lower plasma concentration (90 ng/ml) the corresponding values were 95 and 5% respectively. Although both classes of transcript declined with the decrease in plasma IGF-I, the relative drop in levels of class 2 transcripts (84%) was substantially greater than that of class 1 (54%). In longissimus dorsi, cardiac and soleus muscles IGF-I mRNA was predominantly of class 1 and did not change in response to decreased plasma IGF-I. This suggests that liver-derived endocrine IGF-I has an important function in the regulation of muscle growth and that class 2 IGF-I transcripts are more sensitive to conditions that promote optimal growth.

This article has been cited by other articles:

				M. Katsumata, D. Cattaneo, P. White, K. A. Burton, and M. J. Dauncey Growth Hormone Receptor Gene Expression in Porcine Skeletal and Cardiac Muscles Is Selectively Regulated by Postnatal Undernutrition J. Nutr., October 1, 2000; 130(10): 2482 - 2488. [Abstract] [Full Text]

				A. J. Lewis, T. J. Wester, D. G. Burrin, and M. J. Dauncey Exogenous growth hormone induces somatotrophic gene expression in neonatal liver and skeletal muscle Am J Physiol Regulatory Integrative Comp Physiol, April 1, 2000; 278(4): R838 - R844. [Abstract] [Full Text] [PDF]

				J. M. Brameld, R. S. Gilmour, and P. J. Buttery Glucose and Amino Acids Interact with Hormones to Control Expression of Insulin-Like Growth Factor-I and Growth Hormone Receptor mRNA in Cultured Pig Hepatocytes J. Nutr., July 1, 1999; 129(7): 1298 - 1306. [Abstract] [Full Text]

				K. M. Ohleth, J. A. Lenhart, P. L. Ryan, S. V. Radecki, and C. A. Bagnell Relaxin Increases Insulin-Like Growth Factors (IGFs) and IGF-Binding Proteins of the Pig Uterus in Vivo Endocrinology, September 1, 1997; 138(9): 3652 - 3658. [Abstract] [Full Text] [PDF]