VITAMIN-D METABOLITES AND GROWTH-HORMONE THERAPY IN UREMIC RATS - THESHORT-TERM EFFECT ON GROWTH FAILURE AND HYPERPARATHYROIDISM

The aim of our study was to evaluate the effect of 1,25 dihydroxyvitam in D-3 (D), 22-oxacalcitriol (O) or recombinant human growth hormone ( GH) on growth failure and hyperparathyroidism in 5/6 nephrectomized ur aemic (Ur) rats. Seven groups of rats were studied: (i) sham controls (SC; n = 6); () Ur controls (UrC; n = 8); (iii) Ur treated either with D (UrD; n = 7); (iv) O (UrO, n = 8), (v) GH (UrGH; n = 7); (vi) D + G H (UrDGH; n = 9); or (vii) O + GH (UrOGH; n = 7). For 14 days, D and O were administered intraperitoneally daily at 30 ng/kg per day and GH subcutaneously daily at 1.3 i.u./day. Four weeks after 5/6 nephrectomy , plasma creatinine (Cr), plasma and urine calcium (Ca), plasma phosph ate (P), ratio of urine Ca/urine Cr, amino-terminal parathyroid hormon e (PTH; pg/mL) and Ca/dry bone weight in the left femur (mg/g) were me asured. Uraemic controls, UrD. UrO and UrDGH rats were lower in weight gain than SC rats over the study period, but linear growth was not re tarded in any uraemic group. Plasma Cr was greatly increased in any Ur group as compared with SC group. Plasma Ca and P concentrations did n ot differ among each group. The ratio of urine Cal urine Cr in UrD and UrDGH groups was higher than SC, UrC and UrGH groups. The use of D or D + GH suppressed PTH, returning the level in these rats to the norma l level of the SC rats, while the PTH concentrations in the UrO and Ur OGH rats were less decreased. Bone Ca content was enhanced by D + GH a nd O + GH administration in comparison with UrC rats, but there was no difference in the bone Ca content between UrD and UrDGH rats, and bet ween UrO and UrOGH rats. In conclusion, growth failure in weight was s hown in uraemia, but linear growth was not retarded in any uraemic gro up. 1,25 dihydroxyvitamin D-3 and D plus GH successfully suppressed se condary hyperparathyroidism Further studies are needed in order to elu cidate the interactions on bone between vitamin D metabolites and GH.