Measurements of nuclear size in collecting tubules of the kidney of rats during prolonged hypokinesia and ambulatory conditions.

Hypokinesia (decreased motor activity) induces significant morphological changes in the kidneys, but little is known about the effect of hypokinesia (HK) on the collecting duct nuclei of the kidney. The aim of this study was to measure the effect of prolonged HK on the nuclear size in the inner meduallary collecting ducts on the kidney of rats. Studies were done on one hundred ninety-two 13-week-old male rats (370 to 390 g) during 15 days pre HK period and 90 days HK period. Rats were equally divided into two groups: vivarium control rats (VCR) and hypokinetic rats (HKR). The HKR group kept in small individual cages. Nuclear size in renal collecting tubules, fluid excretion, sodium (Na) and potassium (K) in plasma and urine, plasma aldosterone (PA) and antidiuretic hormone (ADH) and body weight were measured. A significant (p < or = 0.01) increase in size of the collecting duct nuclei of the kidney, PA, plasma and urinary Na and K and fluid loss, and a significant (p < or = 0.01) decrease of body weight and plasma ADH observed in the HKR group when compared with the VCR. The measured parameters did not change significantly in the VCR group when compared with their baseline control values. It was concluded that prolonged HK induces a significant increase of the nuclear size in the inner meduallary collecting ducts of the kidney of hypokinetic rats when compared with the control rats.