Steroid-induced polycystic kidneys in the newborn rat.

The ability of prednisolone, prednisolone tertiary butyl acetate, and tertiary butyl acetate to induce cysts in the kidneys of 8-day-old rats has been examined following single intramuscular injection of the chemicals into newborn rats. The results indicate that only prednisolone tertiary butyl acetate-treated rats developed cysts to any marked extent. The daily injection of potassium chloride (from Day 2 to Day 7) into the prednisolone tertiary butyl acetate-treated rats prevented the formation of cysts. Similar injection of potassium bicarbonate failed to provide protection. Serum and urine electrolyte (potassium, sodium, and chloride) concentrations were also studied on the day of necropsy. The steroid-treated rats did not develop the hypokalemia observed by previous workers. Changes in electrolyte concentrations were noted in a number of instances, but these could not be causally related to cyst formation.