View larger version (12K):
[in a new window]
|
Fig. 6. Effect of dietary P restriction on rate of Pi uptake in the proximal
intestine (open bars) and pyloric caeca (PC; filled bars) of rainbow trout.
Fish were fed either low-P (LP) or high-P (HP) diet for 20 days. Sleeves of
intestine and PC were sampled from the fish at days 2, 5 and 20, and Pi-uptake
analyzed in vitro. Values are means ± S.E.M.
(N=5 fish, 2 tissue sleeves per fish assayed). The tissue incubation
medium contained 0.1 mmol l–1 Pi. At this Pi concentration,
the active component represents  75% of total Pi uptake in PC (see
Fig. 3). Between LP and HP
fish, Pi-uptake was not different at days 2 and 5 in intestine and PC;
however, at day 20, the uptake was markedly different between LP and HP fish
in the intestine (*P=0.002), but not in PC (NS; P=0.35).
Among sampling days (day 2, 5 and 20) in each treatment, Pi uptake was
markedly different in the intestine (ANOVA P=0.001 and 0.03,
regression P=0.0003 and 0.007 in LP and HP fish, respectively), but
not in PC (ANOVA P=0.34 and 0.95, regression P=0.14 and 0.76
in LP and HP fish, respectively).
|
max=64.6±7.6 (mean
± S.E.M.) nmol g tissue–1
min–1; Km=0.474±0.199 mmol
l–1; Kd=0.039±0.002
min–1. In A, percentages of the active component in total Pi
transport were as follows (N=6–10): 99.8 (extrapolation) at
0.28 nmol l–1 (tracer concentration); 74.5±2.6 at 0.1
mmol l–1; 62.7±3.1 at 0.3 mmol l–1;
51.2±6.2 at 0.6 mmol l–1; 56.5±1.9 at 1 mmol
l–1; 45.9±3.0 at 2 mmol l–1;
17.8±8.4 at 5 mmol l–1; 12.5±2.5 at 10 mmol
l–1; and 7.7 (extrapolation) at 20 mmol
l–1.
