Relationship of Serum Somatomedin-Like Activity and Fibroblast Proliferative Activity with Age and Body Weight Gain in Sheep

Abstract

The relationship between serum growth factors and body weight gain was examined in five Dorset lambs. The lambs were weighed and bled by jugular puncture at 2-week intervals between 2 and 18 weeks of age. Somatomedin-like activity (Sm) declined from initially high concentrations at 2 weeks to fairly constant concentrations between 6 and 18 weeks. Relative weight gain--i.e., gain expressed as a percentage of body weight--declined in a manner similar to that of Sm. Mean relative weight gain and mean Sm for the eight 2-week intervals were significantly related (r = .84). Absolute body weight gain--i.e., gain expressed in kilograms--remained fairly constant throughout the study and was not significantly correlated to Sm (r = .15). Serum fibroblast proliferative activity (FPA) was measured as a possible indicator of collective activities of serum growth factors. FPA initially followed a pattern similar to that of Sm, decreasing between 2 and 6 weeks and plateauing until 12 weeks. After 12 weeks, FPA increased to concentrations similar to those observed at 2 weeks. The increase in FPA after 12 weeks was apparently due to an increase in a non-Sm growth factor and had no obvious relationship to body weight changes. Results of the in vitro cell assay system might have been more meaningful if cell type(s) other than WI-38 fibroblasts (e.g., myogenic cells) had been used for estimating collective activities of serum mitogenic factors. The data suggest that serum Sm-like activity may be important in the regulation of growth in sheep.

Correlation of serum GH and IGF-1 with satellite cell responsiveness in Targhee rams

“…This observation held true over the broad range of mean IGF-1 levels detected and is consistent with previous observations in both ruminants and non-ruminants (Davis et al, 1984;Breier et al, 1986). The data presented in Figure 2b suggest that serum IGF-1 levels are not correlated with slaughter weight in the ram and are consistent with those of Olsen et al (1981) and Medrano and Bradford (1991).…”

“…Davis et al (1984) emphasized that the episodic pattern of GH secretion makes it difficult to determine a relationship between GH concentrations and body growth variables. Previous research detected small positive correlations between body weight and serum somatomedin-like activity in lambs (Olsen, Wangsness, Patton and Martin, 1981). Previous research detected small positive correlations between body weight and serum somatomedin-like activity in lambs (Olsen, Wangsness, Patton and Martin, 1981).…”

Validation of a heterologous radioimmunoassay for insulin-like growth factor-I in bovine serum

“…This pattern of increasing serum IGF-I levels during postnatal growth has been reported in pigs (Scanes, Lazarus, Bowen et al 1987), man (Furlanetto et al 1977) and rats (Daughaday, Parker, Borowsky et al 1982). Olsen, Wangsness, Patton & Martin (1981) reported a highly significant correlation between the total serum IGF level and relative weight gain in lambs. Lund-Larsen, Sundby, Kruse & Velie (1977) reported a similar relationship with rate of weight gain in Red Danish bulls.…”

Growth performance and plasma insulin-like growth factor I concentrations in sheep selected for high weaning weight1

“…From this initial report, numerous publications have appeared describing the clinical relevance of IGF-I concentrations in the evaluation of disease states of short stature, growth hormone excess, and nutritional status (Underwood, 1985). A few earlier human studies reported some positive correlations between IGF-I concentrations and growth rates (Gourmelen et al, 1986;Rappaport et al, 1987), but there is no consistent evidence in the literature, even in a recent IGF-I review (Daughaday and Rotwein, 1989), that a positive correlation exists between IGF-I and growth rate in normal individuals.…”