[Importance of estrogen insufficiency time in the efficacy of the bone response to hormonal therapy in experimental chronic renal insufficiency]. / Importancia del tiempo de insuficiencia estrogénica en la eficacia de la respuesta ósea a la terapia hormonal en la insuficiencia renal crónica experimental.

Bone disease develops relatively early in the development of CRF. The aim of this study was to evaluate the repercussion of estrogen insufficiency and the effectiveness of hormonal replacement therapy, after different periods of estrogen deprivation, on bone metabolism in an animal model with chronic renal failure and ovariectomy. A secondary purpose was to evaluate the effectiveness of bone densitometry for predicting changes in bone mass for comparison with bone histomorphometry. We used Sprague-Dawley rats with chronic renal failure and ovariectomy performed at the same time. Animals were divided into two phases according to the period of estrogen insufficiency, 4 weeks in the long estrogen insufficiency period and 1 week in the short estrogen insufficiency period. In both phases, the animals were divided into four treatment groups receiving placebo (corn oil), 17 beta-estradiol (15 micrograms/kg body weight/day), calcitriol (10 ng/kg body weight/day) or the combined treatment with estradiol and calcitriol. In both phases, a group of animals with chronic renal failure (normal ovarian function) was used as a control group. The period of treatment was 8 weeks. After this period the animals were sacrificed. This model emphasizes the importance of the period of estrogen insufficiency in the efficiency of the treatment. Four weeks of estrogen insufficiency resulted in an significant loss of trabecular bone, and less possibility of recovery. After one week of estrogen deprivation a response to the treatment was observed. The utilization of bone densitometry allowed to reproduce changes in bone mass observed afterwards by histomorphometric analysis.

[Chronic renal insufficiency and secondary hyperparathyroidism in rats. Biochemical and histological evaluation]. / Insuficiencia renal crónica e hiperparatiroidismo secundario en ratas: valoración bioquímica e histológica.

Chronic renal failure (CRF) in rats (surgical nephrectomy, 5/6) as well as its derived bone lesions have been studied. Eighty-five male Wistar rats were used, to which chronic renal failure was induced in 1 or 2 surgical times, the parameters of renal function in basal conditions and at different times after surgery being determined. With the method used chronic renal failure is induced with values of creatinine clearance 2/3 times lower than the initial ones (p < 0.05), which stabilize at the 7th week. On the other hand the parathyroid hormone levels (PTH) in serum triple (from 125 +/- 49 to 395 +/- 191, p < 0.05), and a decrease in the tubular phosphate reabsorption is produced (p < 0.001). In bone histology an increase in resorption and bone formation is observed as well as paratrabecular fibrosis, all of which is compatible with the histological diagnosis of hyperparathyroidism. The model of surgical renal insufficiency with ablation of 5/6 of the renal mass, reduces renal function to 1/3 of the initial values after 7 weeks, this procedure having a 20% global mortality without differences being observed between the carrying out of nephrectomies in 1 or 2 surgical times. This degree of CRF was accompanied by secondary hyperparathyroidism both at the biochemical and histological levels, findings which are of great usefulness for future experimental studies.

Prevention of aluminium exposure through dialysis fluids. Analysis of changes in the last 8 years.

Despite extensive measures to control aluminium exposure, chronic and acute episodes of aluminium intoxication still occur. The objective of this study was to analyse the changes in the aluminium content of dialysis fluid and the effect on serum aluminium in different dialysis centres in Spain in the last 8 years. For this purpose, the aluminium content in dialysis fluid and serum samples (N=5609) from 17 dialysis centres was analysed for >8 years (from the last quarter of 1988 to 1996). In that period of time, the percentage of dialysis fluid samples with acceptable concentrations of aluminium (<2 microg/l) increased from 0% in 1988 to 80% in 1996. The percentage of dialysis fluid samples with high aluminium levels (>6 microg/l) ranged between 37.5% in 1988 and 2.3% in 1996. The improvement in the quality of the dialysis fluid resulted in lower values of serum aluminium. The percentage of serum samples with low aluminium (<20 microg/l) increased from 16.5% in 1988 to 54.2% in 1966. The mean serum aluminium correlated with the mean dialysis fluid aluminium (r=0.55, P<0.001). A higher correlation was found when the aluminium in dialysis fluid ranged between 4 and 10 microg/l (r=0.802, P<0.001), and no correlation was found when the aluminium in dialysis fluid was <4 microg/l. Even taking into account that the dialysis fluid is not the only source of aluminium for dialysis patients, our study clearly demonstrated a close relationship with the serum aluminium content. Therefore, we must emphasize the necessity for controlling the aluminium content in dialysis fluid more often than is done at present.