Nephrocalcinosis caused by dietary calcium:phosphorus imbalance in female rats develops rapidly and is irreversible

Female rats fed the standardized AIN-76A diet develop kidney calcium deposits (nephrocalcinosis, NC). A low dietary Ca:P molar ratio is a primary factor in this disorder. The AIN-93G diet has a lower P content and higher Ca:P molar ratio and lowers the incidence of NC. To examine the early stages of NC induced by dietary Ca:P imbalance and the potential reversibility of this disorder, weanling female Sprague-Dawley rats were fed a modified AIN-93G test diet containing Ca:P at AIN-76A levels (NC-inducing diet) for 0.5-16 wk before necropsy, or were switched to AIN-93G control diet after 0.5-4 wk until necropsy at 16 wk. A dramatic increase in incidence and severity of NC was noted after 2 wk of feeding the test diet. NC was not reversible by switching to the control diet. As little as 0.5 wk of exposure to the test diet followed by 15.5 wk of consuming the control diet resulted in increased incidence and severity of NC compared with 16 wk of consuming the control diet. Short-term (as little as several days) feeding of an NC-inducing diet to female rats can lead to NC even if they are switched to an optimal diet.