EVENING PRIMROSE OIL REDUCES URINARY CALCIUM EXCRETION IN BOTH NORMALAND HYPERCALCIURIC RATS

Hypercalciuria is an important risk factor in the aetiology of idiopat hic urolithiasis and many treatment modalities in clinical practice ar e directed towards reducing urinary calcium excreation. There are no n atural animal models of hypercalciuria, such as the spontaneous hypert ensive rat; however, the streptozotocin-diabetic rat is accepted as a good model for studies of disordered renal function associated with di abetes mellitus. Hypercalciuria is a prominent feature of the streptoz otocin-diabetic rat and the model was, therefore, used to study the in fluence of evening primrose oil on urinary clacium excretion. Twenty r ats divided into two groups of ten rats each were maintained on either normal rat chow (group 1) or primrose oil enriched diet (group 2) for 10 weeks. At 4 weeks both groups of rats were made diabetic with stre ptozotocin. Urine calcium measurements were serially performed before commencement of the diet, during the pre-streptozotocin (pre-diabetic) phase and during the post streptozotocin (diabetic) phase. The urine calcium excretion was significantly less in the primrose oil fed anima ls during both the pre-diabetic phase and the diabetic phase compared with the rats on the normal rat chow. These results indicate that even ing primrose oil, a rich source of gamma-linolenic acid, helps to redu ce urine calcium excretion in normal animals as well as in the hyperca lciuric streptozotocin-diabetic rat. Dietary modifications with long-c hain omega-6 and omega-3 fatty acids might be a useful adjunct in the treatment of idiopathic hypercalciuric urolithiasis.