Erythropoietin, 2,3 diphosphoglycerate and plasma volume during moderate-altitude training

Hormonal adjuvants for the treatment of renal anaemia

Hormonal adjuvants, besides being erythropoietic agents, broaden the spectrum of therapeutic options for the treatment of the anaemia of chronic kidney disease (CKD). Lowering elevated parathyroid hormone levels by oral calcium supplementation and phosphate restriction, by varying dialysate calcium concentrations, by administration of vitamin D3 derivatives and, in the near future, by treatment with calcimimetics may prove efficient in some patients to fight extensive requirements of erythropoietic agents. Clinical evidence for a principal role of secondary hyperparathyroidism in resistance to erythropoietin, however, is lacking. Active vitamin D3 derivatives, in addition to their beneficial effects on secondary hyperparathyroidism, appear to exert a direct, stimulatory action on erythroid precursor cells and possibly also an inhibitory action on collagen synthesis by bone marrow stromal cells. Growth hormone (GH) induces insulin-like growth factor (IGF)-1, which in turn counteracts apoptosis similarly to erythropoietin, and fosters proliferation of burst- and colony-forming units-erythroid (BFU-E, CFU-E). If erythropoietic agents improve survival of CKD patients, a similar benefit should apply for strategies that increase synthesis and bioavailabilty of IGF-1. The latter appears to be reduced in CKD patients, and zinc supplementation potentially enhances it via an increase in free IGF-1. Finally, androgens also exert anti-anaemic effects. Nandrolone decanoate constitutes the only androgen currently applicable for selected male dialysis patients over the age of 50 years. It should not be given to women, however, because of serious side effects. Collectively, hormonal interventions offer the potential to reduce requirements of erythropoietic agents, and some may also improve physical performance.

Hypoxia and training-induced adaptation of hormonal responses to exercise in humans

To establish whether or not hypoxia influences the training-induced adaptation of hormonal responses to exercise, 21 healthy, untrained subjects (2) years, mean (SE)] were studied in three groups before and after 5 weeks' training (cycle ergometer, 45 min.day-1, 5 days.week-1). Group 1 trained at sea level at 70% maximal oxygen uptake (VO2max), group 2 in a hypobaric chamber at a simulated altitude of 2500 m at 70% of altitude VO2max, and group 3 at a simulated altitude of 2500 m at the same absolute work rate as group 1. Arterial blood was sampled before, during and at the end of exhaustive cycling at sea level (85% of pretraining VO2max). VO2max increased by 12 (2)% with no significant difference between groups, whereas endurance improved most in group 1 (P < 0.05). Training-induced changes in response to exercise of noradrenaline, adrenaline, growth hormone, beta-endorphin, glucagon, and insulin were similar in the three groups. Concentrations of erythropoietin and 2,3-diphosphoglycerate at rest did not change over the training period. In conclusion, within 5 weeks of training, no further adaptation of hormonal exercise responses takes place if intensity is increased above 70% VO2max. Furthermore, hypoxia per se does not add to the training-induced hormonal responses to exercise.

The effect of short and long duration exercise on serum erythropoietin concentrations

The effects of short and long duration exercise on serum erythropoietin concentrations [EPO]s were studied in seven male cross-country skiers of national team standard and eight male marathon runners, respectively. The short duration exercise was performed as 60 min of cycling at an intensity of 80%-95% of maximal heart rate. Arterial blood oxygen saturations monitored by pulse-oximetry remained unchanged throughout exercise. The partial pressure of O2 at which haemoglobin was half-saturated with O2 calculated from forearm venous blood gas tension and blood O2 saturation, and the erythrocyte 2,3-diphosphoglycerate did not change significantly during the exercise. Blood lactate concentrations were increased at the end of exercise [from 1.3 (SEM 0.1) to 3.6 (SEM 0.3) mmol.l-1]. The [EPO]s determined (by enzyme-linked immunosorbent assay) pre-exercise, 5 min, 6 h, 19 h, and 30 h after the exercise were unchanged [from 16.1 (SEM 2.6) to 19.1 (SEM 3.2), 17.9 (SEM 3.0), 17.0 (SEM 2.5), and 18.6 (SEM 2.9) U.l-1, respectively]. The [EPO]s were not correlated to the earlier parameters. The long duration exercise consisted of habitual training, a 3 week break from training followed by 2 and 4 weeks of re-training. The [EPO]s, body fat (BF), and serum free-testosterone concentrations determined at the end of each period remained unchanged. The maximal oxygen uptakes were decreased after the break from training and increased during retraining (P = 0.04). Body mass (mb) increased after the break in training (P = 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)