Fig. 4.
Time course of deuterium enrichments in serum water, free alanine in serum, alanine in serum proteins, and alanine in tendon and liver proteins after removal of 2H water input. All rats consumed 2H2O for the first 42 days and then plain tap water thereafter. The data start on day 42. ◆, Serum water 2H enrichments (n = 4/time point); dotted line is the fitted exponential curve (k = 18.03 ± 0.22%/day). △, Serum-free alanine 2H enrichments (n = 2–3/time point); dashed line is the fitted exponential curve (kAla = 17.94 ± 0.82%/day). Gray triangles, serum protein-bound alanine 2H enrichments (n = 4/time point); solid line is the fitted exponential curve (k = 9.93 ± 0.58%/day). ▫, Tissue protein-bound alanine 2H enrichments for nonsoluble mixed liver proteins. ○, Tissue protein-bound alanine 2H enrichments for tendon collagen proteins. Values are means ± SE, although the error bars may be smaller than the symbols at some time points. The serum water and serum-free alanine enrichments overlap at several time points.