Performance during a strenuous swimming session is associated with high blood lactate: pyruvate ratio and hypoglycemia in fasted rats

Abstract

The aim of this study was to investigate the effect of lactatemia elevation and glycemia reduction on strenuous swimming performance in fasted rats. Three rats were placed in a swimming tank at the same time. The first rat was removed immediately (control group) and the remaining ones were submitted to a strenuous swimming session. After the second rat was exhausted (Exh group), the third one was immediately removed from the water (Exe group). According to the period of time required for exhaustion, the rats were divided into four groups: low performance (3–7 min), low-intermediary performance (8–12 min), high-intermediary performance (13–17 min), and high performance (18–22 min). All rats were removed from the swimming tanks and immediately killed by decapitation for blood collection or anesthetized for liver perfusion experiments. Blood glucose, lactate, and pyruvate concentrations, blood lactate/pyruvate ratio, and liver lactate uptake and its conversion to glucose were evaluated. Exhaustion in low and low-intermediary performance were better associated with higher lactate/pyruvate ratio. On the other hand, exhaustion in high-intermediary and high performance was better associated with hypoglycemia. Lactate uptake and glucose production from lactate in livers from the Exe and Exh groups were maintained. We concluded that there is a time sequence in the participation of lactate/pyruvate ratio and hypoglycemia in performance during an acute strenuous swimming section in fasted rats. The liver had an important participation in preventing hyperlactatemia and hypoglycemia during swimming through lactate uptake and its conversion to glucose.

Strenuous swimming raises blood non-enzymatic antioxidant capacity in rats

“…Additionally, our results demonstrates that a strenuous swimming session increased plasma lactate concentrations and the lactate:pyruvate ratio, an observation that was consistent with previous studies (15,26). The increased lactate:pyruvate ratio is indicative of changes in the redox state (i.e., NADH:NAD + ratio) after exercise and exhaustion in the Nex and Pex groups.…”

“…For many years, lactate was considered a metabolic residue (28,29). It is currently recognized for its role as a liver glucose precursor (15), an angiogenesis signal (28), an oxidative substrate in neurons (30), a memory consolidation molecule (31), and an antioxidant in human cells (32)(33)(34). Today, the well-established role of lactate as an antioxidant justifies its use as a food preservative (35).…”

“…The swimming session was performed in cylindrical tanks (60 Â 30 cm, 30 L capacity) with a water temperature of 31 ± 1°C. Before each session, a load corresponding to 6% of the body weight was tied to the tail of the animals (15).…”

“…When the first rat was exhausted (NexExh), the second rat was also removed from the water (NexExe). Exhaustion was defined as failure to stay above the water surface, loss of symmetrical movements, and/or remaining underwater for more than 5 s (15). The control group (Nex-Control) consisted of overnight-fasted rats that were placed in the swimming tank and immediately removed.…”

“…The redox state, especially antioxidant defenses, in exercising experimental animals and humans has been extensively studied (3,8,11,13). However, these studies employed various exercise intensities, durations, and training schedules, with participants of both genders and different ages (8)(9)(10)(11)(13)(14)(15). Consequently, this heterogeneity limits and jeopardizes the evaluation of the role of antioxidant defenses during strenuous exercise.…”