Phosphate measurements during hypokinesia and phosphate supplements in disclosing phosphate changes in hypokinetic...

Hypokinesia (diminished movement) induces significant phosphate (P) change, however, little is known about P retention and P depletion during hypokinesia (HK). Measuring P retention and P balance during HK and P supplementation, the objective of this work was to disclose whether HK could contribute to the decreased P retention and consequently to P depletion in normal subjects.

Studies were done during 30 days pre-HK period and 364 days HK period. Forty normal male individuals aged, 25.3+/-6.4 years were chosen as subjects. They were divided equally into 4 groups: unsupplemented active control subjects (UACS), unsupplemented hypokinetic subjects (UHKS), supplemented active control subjects (SACS) and supplemented hypokinetic subjects (SHKS). Hypokinetic subjects were limited to an average walking distance of 0.5 km day-l, while active control subjects were kept on an average running distance of 9.6 km day-l. Both, SHKS and SACS received daily 14 mmol dicalcium phosphate per kg body weight.

Negative P balance, fecal P, urinary calcium (Ca) and P excretion, serum P and total (Cat) level increased significantly (p<0.05) while P retention, serum intact parathyroid hormone (iPTH), 1,25 dihydroxyvitamin D (1,25 (OH)2 D3) and thyrocalcitonin (TC) decreased significantly (p<0.05) in SHKS and UHKS compared with their pre-HK values and their respective active controls (SACS and UACS). However, negative P balance, P retention incapacity, serum, fecal and urinary P level increased significantly (p<0.05) more in SHKS compared with UHKS. Fecal P loss, urinary P and Ca loss, serum P and Cat level, iPTH, TC and 1,25 (OH)2 D3 level, P retention and P balance change insignificantly (p>0.05) in SACS and UACS compared with their pre-HK level.

It was concluded that a significant P excretion in urine and feces in spite of negative P balance and P supplementation may demonstrate reduced P retention, while a significant increase of negative P balance may demonstrate P depletion. Clearly, P intake, regardless of its low or higher dose, was significantly wasted during HK probably due to the decreased ability of the body to retain P.