Meeting Abstract

P1.77  Sunday, Jan. 4  Food Restriction Inhibits Growth Rate but Not Expression of Hepatic IGF-I Message in Yarrows Spiny Lizard, Sceloporus jarrovii DUNCAN, C.A.**; JOHN-ALDER, H.B.; Rutgers Univ., New Brunswick; Rutgers Univ., New Brunswick caduncan@eden.rutgers.edu

The growth hormone/insulin-like growth factor-I axis is the central growth regulatory axis in vertebrates, and nutrition is a major regulator of this axis. In particular, the growth-promoting actions of GH are primarily mediated by IGF-I. To determine the effects of nutrition on growth and the expression of hepatic IGF-I message, captive male and female Sceloporus jarrovii were fed diets of high food (3 crickets/d) and low food (1 cricket/d) availabilities for a 10-week treatment period. We predicted that food restriction would inhibit growth and decrease the expression of hepatic IGF-I message in comparison to high food availability. In the present study, food restriction inhibited growth rate by about 50% in snout-vent length (SVL) and decreased mass of fat bodies relative to high food availability. At the conclusion of the treatment period, levels of plasma corticosterone (B) did not differ between treatment groups, but the low-food group had higher production of basal B in adrenocortical cells relative to the high-food group. Taken together, these data demonstrate that food restriction did not chronically stress animals in either treatment group. Furthermore, food restriction did not decrease the relative expression of hepatic IGF-I message compared to high food availability. Although differing levels of available nutrition led to dramatic differences in growth between treatment groups, these results indicate that the food regimen in this study was not sufficient to elicit a response that would negatively regulate the GH/IGF-I axis at the level of hepatic IGF-I message. Future studies will need to be designed such that the nutritional treatment produces a negative energy balance. Supported by NSF (IBN 0135167 to HBJ-A).