Responses to divergent selection for plasma concentrations of insulin-like growth factor-1 in mice.
A divergent selection experiment with mice, using plasma concentrations of insulin-like growth factor-1 (IGF-1) at 42 days of age as the selection criterion, was undertaken for 7 generations. Lines were not replicated. To obtain sufficient plasma for the IGF-1 assay, blood from four individuals was volumetrically bulked to obtain a litter mean IGF-1 concentration. This necessitated the use of between family selection. Although inbreeding accumulated in a linear fashion in each of the high, control and low lines, the rates were different for each line (3.6, 1.6 and 5.3% per generation for the high, control and low lines, respectively). As a consequence, the effects of selection and inbreeding are confounded in this experiment. Divergence between the high and low lines in plasma concentrations of IGF-1 continued steadily until generation 5. In generations 6 and 7, there was a reduced degree of divergence and this contributed towards the low realized heritability value of 0.15 +/- 0.12. Six-week liveweight showed a steady positive correlated response to selection for or against plasma concentrations of IGF-1 until generation 4 (high-low difference = 1.7 g = 12%). In generation 5, a substantial drop in 6-week liveweight in the low line relative to both the high and control lines occurred (high-low difference, 3.9; g, 25%). This difference was maintained until generation 7.(ABSTRACT TRUNCATED AT 250 WORDS)
Blair
H T
HT
McCutcheon
S N
SN
Mackenzie
D D
DD
Gluckman
P D
PD
Ormsby
J E
JE
Brier
B H
BH
D000818:Animals; D001835:Body Weight; D005260:Female; D014644:Genetic Variation; D007334:Insulin-Like Growth Factor I / Q000097:blood / Q000235:genetics*; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D012641:Selection, Genetic; D013002:Somatomedins / Q000235:genetics*
D013002:Somatomedins; D007334:Insulin-Like Growth Factor I