The purpose of this study was to examine the influence of exercise on the serum concentrations of intact parathyroid hormone (PTH). Serum PTH and plasma lactate were measured in 15 well-trained men, 9 long-distance runners and 6 fire-fighters, during two running exercises. Test one consisted of 40-minute treadmill running with a step-wise increased load and test two consisted of 50-minute treadmill running with a constant velocity. When the load was step-wise increased, the PTH concentrations increased moderately at the slower running paces but reached a final value that was about 50% higher than the starting value. This rise occurred despite a concomitant increase of total serum calcium from 2.38 +/- 0.06 to 2.49 +/- 0.05 mmol/liter (P < 0.01). During the constant running exercise, the long-distance runners, but not the fire-fighters, displayed a significant increase in PTH concentrations although the rise in total serum calcium was similar in both groups. There was a weak correlation between the changes in PTH and lactate in both exercises. The findings demonstrate that both high and low intensity exercise enhance release of PTH in long-distance runners through a mechanism that does not involve serum calcium. This relationship might be of importance for bone mass in men performing long-distance training.

This paper has for its purpose the presentation of data obtained from the analysis of blood serum and transudates from human subjects, and an examination of these data to determine whether the distribution of electrolytes in these systems is adequately defined by the laws first stated by Willard Gibbs, afterwards elaborated and tested by F. G. Donnan, and lately applied to protein solutions by Jacques Loeb. Van Slyke, Wu, and McLean showed in 1923 that the unequal distribution of bicarbonate and chloride ions between the serum and erythrocytes of horse blood, equilibrated at fixed CO2 tensions, was in harmony with the ratios predicted by the GibbsDonnan law. Calculations made at that time from the data of Loeb, Atchley, and Palmer of the distribution of electrolytes between serum and transudates suggested that these were systems which were in approximate equilibrium and to which the Donnan law could be applied. Except in the case of the chloride ratios, however, discrepancies of considerable magnitude existed between the distribution found by analysis and that predicted by the formulae developed by Van Slyke, Wu, and McLean. The data in this paper present further experimental evidence on the question of whether serum and transudates constitute a heterogeneous system in appro~dmate thermodynamic equilibrium; and whether the membrane separating them is freely diffusible to inorganic anions and cations as is collodion, or whether it has properties of selective permeability as has the red cell membrane.

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Change in levels of the carboxyteminal propeptide of type I procollagen, the carboxyterminal cross-linked telopeptide o type I collagen and osteocalcin in response exercise in well-trained men and women response exercise in well-trained men and women propeptide of type carboxyterminal cr type I collagen and I '0 ' ( procollagen, lss-linked telo >steocalcin in the peptide o Salvesen H, Piehl-Aulin K, Ljunghall S. Change in levels of the carboxyterminal propeptide of type I procollagen, the carboxyterminal cross-linked telopeptide of type I collagen and osteocalcin in response to exercise in well-trained men and women. Scand J Med Sci Sports 1994: 4: 186-190. Q Munksgaard, 1994 Physical exercise preserves bone mass. Measurements of bone biomarkers may reflect the events in bone during exercise. Fifteen healthy, well-trained individuals (7 men and 8 women) performed a running test for 21 min until exhaustion. Venous blood samples were drawn before and 30 min after the exercise to measure the levels of osteocalcin, the carboxyterminal propeptide of type I procollagen (PICP) and the carboxyterminal crosslinked telopeptide of type I collagen (ICTP). After exercise, the women had a marked increase in serum osteocalcin concentrations (from 7.525.0 pgll to 11.523.0 pd), whereas the level was unaffected in the men (from 14.523.0 pgll to 13.524.6 pd). In the men there was a marked increase in PICP (from 240247 pgA to 268+56 pgll) that was not seen in the women (from 244270 pgA to 253260 pgA). In neither group did ICTP levels change. In conclusion, significant responses were seen in PICP and osteocalcin during exercise, indicating that such measurements may be valuable for the further delineation of the effects of physical activity on bone. Furthermore, the different responses in men and women point to interesting areas for future studies.Physical exercise is known to preserve bone mass (1, 2) but the underlying mechanisms are not clarified. Direct mechanical effects of weight-bearing (3) as well as hormonal factors could be of importance (1). Bone biomarkers reflect the cellular events in bone (4) but have hitherto been little used for studies of the relationship between exercise and bone.Osteocalcin is a non-collagenous protein synthesized by osteoblasts. It binds to bone mineral and is also released into the circulation, where it indicates bone formation (5). The carboxyterminal propeptide of type 1 procollagen (PICP) is released to the circulation when type I collagen is synthesized and is therefore related to bone synthesis (6-9). The carboxytednal cross-linked telopeptide of type I collagen (ICTP) is liberated during the degradation of type I collagen and is believed to be a specific and sensitive marker of bone resorption (7, 10, 11).We measured these biomarkers in well-trained individuals before and after treadmill running until exhaustion. Materlal and methods SubjectsFifteen he.althy, well-trained cross-country runners (8 women and 7 men) gave informed consent to participate in the study. Data for all subjects a...