Evaluation of four animal models of intrarenal calcium deposition and assessment of the influence of dietary supplementation with essential fatty acids on calcification.

Firstly, to determine a satisfactory animal model for induction of intrarenal calcification, a study of four previously described animal models of intrarenal calcification was carried out which showed that intraperitoneal injection of 10% calcium gluconate into female Sprague-Dawley rats was most effective. We then investigated the hypothesis that dietary supplementation with essential fatty acids could reduce the intrarenal calcification developing as a result of intraperitoneal calcium injection. Using a combination of fish oil and evening primrose oil, we demonstrated a significant difference in renal parenchymal calcification, which was 940 +/- 240 micrograms Ca/g dry weight renal parenchyma in unsupplemented animals and 320-370 +/- 55-65 micrograms Ca/g dry weight renal parenchyma in supplemented animals (means +/- SEM, P < 0.005). It was also demonstrated that there was synergism between eicosapentaenoic acid (EPA) and gamma-linolenic acid (GLA): dietary supplementation with a combined oil preparation containing 27 mg/ml EPA and 67 mg/ml GLA mixed as 2% with food was as effective as oils containing either 400 mg/ml EPA or 80 mg/ml GLA mixed as 4% of food.