Table 1.
Parameters of lactate kinetics and isotopic enrichment ratios during control, exogenous lactate load, and epinephrine stimulation conditions
| Con | LC | Epi | |
|---|---|---|---|
| v̄-a difference mM | 0.4 (0.2) | 0.6 (0.7) | 0.2 (0.5)§ |
| Net lactate balance, mg/min | 1.2 (0.7) | 1.9 (2.5) | 1.9 (3.5) |
| FEXC, % (net balance) | 19.4 (11.1) | 11.8 (13.9) | 8.2 (21.6) |
| FEXTM, % (tracers) | 16.6 (15.3) | 8.2 (15.3) | −25.3 (45.5)*§ |
| P → L, μmol/min | 12.8 (24.8) | ||
| Lactate total release, mg/min | −0.3 (1.6) | −0.9 (3.2)* | −6.9 (10.2)*§ |
| Lactate Ra, mg/min | 1.2 (0.3) | 8.4 (1.9)* | 3.3 (1.6)*§ |
| Lactate Rd, mg/min | 1.2 (0.3) | 8.4 (1.9)* | 3.3 (1.6)*§ |
| Lactate MCR, ml/min | 8.6 (2.8) | 21.4 (2.7)* | 12.6 (4.1)§ |
| % Lung lactate turnover of whole body | 5.1% | 12.9% | 43.0%*§ |
| L/P concentration ratio Δ (a-v̄) | 28.4 (0.6) | 16.2 (0.1) | 39.6 (2.6) |
| Mixed central venous IEL/IEP | 2.6 (1.3) | 3.6 (1.8) | 2.2 (1.2) |
| Arterial IEL/IEP | 1.3 (1.8) | 2.9 (0.9)* | 3.2 (0.8) |
Values are expressed as means and SD (SD). Con, control; LC, lactate load; Epi, epinephrine stimulation; FEXC, fractional extraction from concentration; FEXTM, tracer-measured fractional extraction; Ra, rate of appearance; Rd, rate of disappearance; L/P, lactate to pyruvate; IEL, isotopically enriched lactate; and IEP, isotopically enriched pyruvate.
*
Significantly different than Con, P < 0.05.
§
Significantly different than LC, P < 0.05.