Atrial natriuretic peptide and the renin-aldosterone axis during exercise in man

Does the Minerals Content and Osmolarity of the Fluids Taken during Exercise by Female Field Hockey Players Influence on the Indicators of Water-Electrolyte and Acid-Basic Balance?

Although it is recognized that dehydration and acidification of the body may reduce the exercise capacity, it remains unclear whether the qualitative and quantitative shares of certain ions in the drinks used by players during the same exertion may affect the indicators of their water–electrolyte and acid–base balance. This question was the main purpose of the publication. The research was carried out on female field hockey players (n = 14) throughout three specialized training sessions, during which the players received randomly assigned fluids of different osmolarity and minerals contents. The water–electrolyte and acid–base balance of the players was assessed on the basis of biochemical blood and urine indicators immediately before and after each training session. There were statistically significant differences in the values of all examined indicators for changes before and after exercise, while the differences between the consumed drinks with different osmolarities were found for plasma osmolality, and concentrations of sodium and potassium ions and aldosterone. Therefore, it can be assumed that the degree of mineralization of the consumed water did not have a very significant impact on the indicators of water–electrolyte and acid–base balance in blood and urine.

Changes in Plasma Aldosterone and Electrolytes Following High-Volume and High-Intensity Resistance Exercise Protocols in Trained Men

Boone, CH, Hoffman, JR, Gonzalez, AM, Jajtner, AR, Townsend, JR, Baker, KM, Fukuda, DH, and Stout, JR. Changes in plasma aldosterone and electrolytes following high-volume and high-intensity resistance exercise protocols in trained men. J Strength Cond Res 30(7): 1917-1923, 2016-Program variables such as training intensity, volume, and rest interval length are known to elicit distinct hormonal, metabolic, and physical responses. However, little is known regarding resistance exercise (RE) program design and the fluid regulatory response. This investigation aimed to compare the plasma aldosterone (ALD), electrolyte, plasma volume (PV), and osmolality (Posm) responses following high-volume (HV; 4-6 × 10-12 reps, 70% 1 repetition maximum [1RM], 60-s rest) and high-intensity (HI; 6 × 3-5 reps, 90% 1RM, 180-second rest) RE protocols. Ten experienced, resistance-trained men (24.7 ± 3.4 years; 90.1 ± 11.3 kg; 176.0 ± 4.9 cm) performed each protocol in a random, counterbalanced order. Blood samples were obtained at baseline (BL), immediately (IP), 30 minutes (30P), and 1 hour (1H) postexercise. Significant trial × time interactions (p < 0.01) were observed in Posm, sodium (Na), and potassium (K), whereas a trend (p = 0.06) was observed for ALD. The PV shift from BL-30P was greater than BL-IP and BL-1H (p ≤ 0.05), but no significant between-trial differences were noted. Comparisons between RE protocols revealed significantly greater (p ≤ 0.05) elevations during HV vs. HI in Posm at IP, 30P, and 1H; and Na at IP and 30P. During HV, significant reductions (p ≤ 0.05) were noted in K at IP compared with HI. Area under the curve analysis indicates a trend (p = 0.07) toward a higher ALD response following HV compared with HI. Results of this study indicate that high-volume, moderate-intensity resistance exercise seems to augment the fluid regulatory response to a greater extent than low-volume, high-intensity training.

Hormonal responses and adaptations to resistance exercise and training

Resistance exercise has been shown to elicit a significant acute hormonal response. It appears that this acute response is more critical to tissue growth and remodelling than chronic changes in resting hormonal concentrations, as many studies have not shown a significant change during resistance training despite increases in muscle strength and hypertrophy. Anabolic hormones such as testosterone and the superfamily of growth hormones (GH) have been shown to be elevated during 15-30 minutes of post-resistance exercise providing an adequate stimulus is present. Protocols high in volume, moderate to high in intensity, using short rest intervals and stressing a large muscle mass, tend to produce the greatest acute hormonal elevations (e.g. testosterone, GH and the catabolic hormone cortisol) compared with low-volume, high-intensity protocols using long rest intervals. Other anabolic hormones such as insulin and insulin-like growth factor-1 (IGF-1) are critical to skeletal muscle growth. Insulin is regulated by blood glucose and amino acid levels. However, circulating IGF-1 elevations have been reported following resistance exercise presumably in response to GH-stimulated hepatic secretion. Recent evidence indicates that muscle isoforms of IGF-1 may play a substantial role in tissue remodelling via up-regulation by mechanical signalling (i.e. increased gene expression resulting from stretch and tension to the muscle cytoskeleton leading to greater protein synthesis rates). Acute elevations in catecholamines are critical to optimal force production and energy liberation during resistance exercise. More recent research has shown the importance of acute hormonal elevations and mechanical stimuli for subsequent up- and down-regulation of cytoplasmic steroid receptors needed to mediate the hormonal effects. Other factors such as nutrition, overtraining, detraining and circadian patterns of hormone secretion are critical to examining the hormonal responses and adaptations to resistance training.

Effects of human pregnancy on fluid regulation responses to short-term exercise

This study tested the hypothesis that human pregnancy alters fluid and electrolyte regulation responses to acute short-term exercise. Responses of 22 healthy pregnant women (PG; gestational age, 37.0 +/- 0.2 wk) and 17 nonpregnant controls (CG) were compared at rest and during cycling at 70 and 110% of the ventilatory threshold (VT). At rest, ANG II concentration was significantly (P < 0.05) higher in PG vs. CG, whereas plasma osmolality and concentrations of AVP, sodium, and potassium were significantly lower. Atrial natriuretic peptide concentration at rest was similar between groups. ANG II and AVP concentrations increased significantly from rest to 110% VT in CG only, whereas increases in atrial natriuretic peptide concentration were similar between groups. Increases in osmolality, and total protein and albumin concentrations from rest to both work rates were similar between the two groups. PG and CG exhibited similar shifts in fluid during acute short-term exercise, but the increases in ANG II and AVP were absent and attenuated, respectively, during pregnancy. This was attributed to the significantly augmented fluid volume state already present at rest in late gestation.

Enhanced brain natriuretic peptide response to peak exercise in heart transplant recipients

We investigated the atrial (ANP) and brain natriuretic peptides (BNP), catecholamines, heart rate, and blood pressure responses to graded upright maximal cycling exercise of eight matched healthy subjects and cardiac-denervated heart transplant recipients (HTR). Baseline heart rate and diastolic blood pressure, together with ANP (15.2 +/- 3.7 vs. 4.4 +/- 0.8 pmol/l; P < 0.01) and BNP (14.3 +/- 2. 6 vs. 7.4 +/- 0.6 pmol/l; P < 0.01), were elevated in HTR, but catecholamine levels were similar in both groups. Peak exercise O2 uptake and heart rate were lower in HTR. Exercise-induced maximal ANP increase was similar in both groups (167 +/- 34 vs. 216 +/- 47%). Enhanced BNP increase was significant only in HTR (37 +/- 8 vs. 16 +/- 8%; P < 0.05). Similar norepinephrine but lower peak epinephrine levels were observed in HTR. ANP and heart rate changes from rest to 75% peak exercise were negatively correlated (r = -0.76, P < 0.05), and BNP increase was correlated with left ventricular mass index (r = 0.83, P < 0.01) after heart transplantation. Although ANP increase was not exaggerated, these data support the idea that the chronotropic limitation secondary to sinus node denervation might stimulate ANP release during early exercise in HTR. Furthermore, the BNP response to maximal exercise, which is related to the left ventricular mass index of HTR, is enhanced after heart transplantation.

Relationships between fluid and electrolyte hormones and plasma volume during exercise with training and detraining

PURPOSE

The purpose of this study was to investigate the relationship between training-induced alterations in plasma volume (PV) and changes in fluid and electrolyte regulatory hormones during prolonged exercise.

METHODS

Seven male subjects (VO2peak 49.2 +/- 2.4 mL.kg-1.min-1, X +/- SE) performed a cycling test before (C) and after (T) 6 d of training and after 6 d of detraining (DT). Training was conducted for 2 h.d-1 at 68% VO2peak at a room temperature between 26-28 degrees C. The 60-min exercise challenge included 20 min at 50%, 65%, and 75% VO2peak workloads.

RESULTS

Training resulted in a calculated 13.8 +/- 1.6% PV expansion (P < 0.05) which recovered to C levels with DT (1.8 +/- 2.3%, P > 0.05). Compared with that at C, training resulted in a reduction of aldosterone (ALDO) concentration at all exercise intensities (P < 0.05) which normalized to C levels with DT. With T, epinephrine (EPI) concentrations were reduced at the highest power output only (365 +/- 51 vs 113 +/- 22 pg.mL-1; P < 0.05) and returned to C levels with DT. Arginine vasopressin (AVP) concentrations were also reduced at the highest workload only (20.2 +/- 3.2 pg.mL-1 vs 10.4 +/- 0.7 pg.mL-1; P < 0.05) and remained depressed after DT (11.8 +/- 1.3 pg.mL-1; P < 0.05). Atrial natriuretic factor (ANF) and norepinephrine (NOREPI) were not affected by T or DT.

CONCLUSIONS

The results suggest that concentrations of ALDO, and to a lesser extent EPI, during exercise are related to PV levels, whereas ANF and NOREPI concentrations are not. AVP concentrations are related to other adaptive factors, the effects of which persist for a longer time course than do PV changes.

Restricted postexercise pulmonary diffusion capacity and central blood volume depletion

Pulmonary diffusion capacity for carbon monoxide (DLCO), regional electrical impedance (Z0), and the distribution of technetium-99m-labeled erythrocytes together with concentration of plasma atrial natriuretic peptide (ANP) were determined before and after a 6-min "all-out" row in nine oarsmen and in six control subjects. Two and one-half hours after exercise in the upright seated position, DLCO was reduced by 6 (-2 to 21; median and range) %, the thoracic-to-thigh electrical impedance ratio (Z0 thorax/Z0 thigh) rose by 14 (-1 to 29) %, paralleled by a 7 (-3 to 11) % decrease and a 3 (-5 to 12) % increase in the thoracic and thigh blood volume, respectively. These responses were associated with a decrease in the plasma ANP concentration from 15 (13-31) to 12 (9-27) pmol/l (P < 0.05). Similarly, in the supine position, Z0 thorax/Z0 thigh increased by 10 (-5 to 28) % when DLCO was reduced 12 (6-26) % (P < 0.05), whereas DLCO remained stable in the control group. The increase in Z0 thorax/Z0 thigh and the corresponding redistribution of the blood volume in both body positions show that approximately one-half of the postexercise reduction of DLCO is explained by a decrease in the pulmonary blood volume. The role of a reduced postexercise central blood volume is underscored by the lower plasma ANP, which aids in upregulating the blood volume after exercise in athletes.

Fluid and electrolyte hormonal responses to exercise and acute plasma volume expansion

To investigate the effect of acute graded increases in plasma volume (PV) on fluid and regulatory hormone levels, eight untrained men (peak aerobic power 45.2 +/- 2.2 ml.kg-1.min-1) performed prolonged cycle exercise (46 +/- 4% maximal aerobic power on three occasions, namely, with no PV expansion (Con) and after 14% (Low) and 21% (High) expansions, respectively. The exercise plasma levels of aldosterone (Aldo), arginine vasopressin (AVP), and atrial natriuretic peptide (ANP) were all altered by acute PV increases. A pronounced blunting (P < 0.05) of the Aldo response during exercise was observed, the magnitude of which was directly related to the amount of hypervolemia (Con < Low < High). At 120 min of exercise, Aldo concentrations were 660 +/- 71, 490 +/- 85, and 365 +/- 78 pg/ml for Con, Low, and High conditions, respectively. In contrast, the lower AVP and the higher ANP observed during exercise appeared to be due to the effect of PV expansion on resting concentrations. Because osmolality did not vary among conditions, the results indicate that PV represents an important primary stimulus in the response of Aldo to exercise. The lower exercise blood concentrations of both epinephrine and norepinephrine observed with PV expansion would suggest that a lower sympathetic drive may be implicated at least in the lower Aldo responses.

Atrial natriuretic factor responses to submaximal and maximal exercise

The aim of this study was to evaluate and compare the plasma concentration of atrial natriuretic factor (ANF), K+, Na+, blood lactate, heart rate, and blood pressure in moderately trained women. Ten healthy women were studied on a cycle ergometer during 20 min of constant submaximal and maximal exercise, as well as during recovery. The ANF concentration was determined by radioimmunoassay. The results show that, except for Na+, all the other variables increased significantly with an increase in the duration and intensity of the exercise (P < 0.05, P < 0.001). In recovery, the values fell (P < 0.01, P < 0.001). Submaximal and maximal exercise both cause increases in ANF and this increase is due to the duration and intensity of exercise. However, maximal exercise, rather than submaximal exercise, is the major stimulus for the concentration of plasma ANF. ANF concentration may be a useful test for evaluating the releasing function of ANF in the heart.

Plasma ANP and cyclic GMP after physical exercise in patients with mitral valve disease and in healthy subjects

Plasma levels of both atrial natriuretic peptide (ANP) and cyclic GMP are elevated in patients with various heart diseases as compared to healthy subjects. In this study patients with advanced mitral valve disease (Group A) and healthy subjects (Group B) were exposed to symptom-limited upright stepwise physical exercise on a cycle ergometer. Concentrations of ANP and cyclic GMP were measured in plasma at rest (20 min in supine position) or 5 min after physical exercise by specific radioimmunoassays. Here we show that short dynamic exercise caused a significant increase in plasma levels of ANP and cyclic GMP, in both groups. In Group A strong correlation between plasma ANP and cyclic GMP was found at rest (r = 0.91, P < 0.001, n = 11) and after physical exercise (r = 0.85, P < 0.001, n = 11). In contrast, there was no correlation between plasma concentrations of ANP and cyclic GMP in Group B at rest (r = -0.16, P > 0.05, n = 10) or after exercise loading (r = 0.14, P > 0.05, n = 10). Absolute increases in circulating levels of both substances were not found to correlate in either group. These data suggest that exercise-induced elevations in plasma cyclic GMP may be due not only to ANP release but also to an as yet undetermined factor, possibly EDRF/NO.

The effect of oxygen with exercise on atrial natriuretic peptide in chronic obstructive lung disease

A recent study on stable, hypoxemic, COLD patients in which ANP was stimulated by LBPP demonstrated that in these individuals elevation of ANP does not exert a "normal" suppressing effect on the PRA-PA axis. Accordingly, we exercised ten comparable COLD patients, another maneuver known to stimulate ANP and to elicit cardiorespiratory responses substantially different from those observed with LBPP. Patients were studied breathing room air and on 40 percent O2 to determine whether the level of oxygenation would modify ANP secretion. Basal levels of ANP on room air were markedly elevated above controls (269 +/- 65 SE vs 70 +/- 20 pg/ml, p less than 0.05); PRA (13.0 +/- 5.4 ng/ml/90 min) and PA (8.6 +/- 3.5 ng/100 ml) were elevated (greater than 2 SD over control levels of 8.1 +/- 1.3 and 2.6 +/- 0.7) in 6/10 and 2/10 patients, respectively. During exercise while breathing O2, only ANP increased; PRA and PA remained unchanged when breathing air and O2. Comprehensive statistical analyses failed to demonstrate a negative relationship between ANP and PRA or ANP and PA. We conclude that in patients with advanced COLD, ANP response to moderate exercise is significantly affected by correction of hypoxemia. This effect may be mediated through changes in airway resistance and consequently cardiac filling pressure.