The Effect of Dietaty Protein Level on the Ca and Bone Metabolism in Ovariectomized Rat

난소를 절제한 흰쥐에서 식이 단백질 수준이 체내 Ca 및 골격 대사에 미치는 영향

To study the effect of menopause and dietary protein level on Ca metabolism, ovariectomy (OVAX) and sham operations were performed in 16-week old female rats. Each treatment group was fed for 16 weeks either 5%(L) or 50%(H) casein diets, forming SH, SL, OH, OL groups. High protein groups(SH, OH) showed higher Ca and hydroxyproline excretion in urine. Urinay hydroxyproline was also higher in OVAX, which tells the possibility of increased bone resorption by OVAX and by high dietary protein. At 16th wee, however, urinary Ca and hydroxyproline of SH caught up with OH group, whereas those of OL remained higher than SL. Therefore it seems that high dietary protein overrides the effect of OVAX with time. Urnary protein measured at 8th week was higher in high protein groups, especially in OH. GFR was not differ significantly among groups at 8th week. At 16th week, however, high protein groups showed twice the GFR value of low protein groups. Therefore the increase of urinary Ca and hydroxyproline in SH and OH groups can be explained partly by the increased GFR. The tendency of increased GFR and urinary excretion of protein, Ca, and hydroxyproline was most obvious in OH group. It seems that the effect of high protein diet is likely to accelerated by ovariectomy. The effect of Ovax and dietary protein on the composition of femur, scapular, and lumbar bones, was not pronounced. However, when only the high protein groups were compared, OVAX resulted in the reduction of bone weight, ash and Ca contents, especially in femur. The reason that was no significant effect on bone might be due to the short experimental period to induce that was no significant effect on bone might be due to the short experimental period to induce the changes on bone composition and dietary Ca content used in this experiment may have been high enough to prevent bone loss.