Method for studying the in vivo accumulation of inorganic mercury in segments of the nephron in the kidneys of rats treated with mercuric chloride

Abstract

A method for studying the in vivo accumulation of inorganic mercury along the nephron of Sprague-Dawley rats pretreated with a radiolabelled 0.66 μmol/kg dose of mercuric chloride is described in this article. Forty-eight hr after rats received the radiolabelled dose of mercuric chloride intravenously the kidneys of the animals were perfused in situ with a collagenase solution in order to dissect and isolate various readily assessable segments of the nephron and collecting duct. Three different categories of tubular segments were isolated; proximal convoluted tubules, proximal straight tubules and combined segments of the distal nephron and collecting duct. A group of isolated tubular segments were measured in length, drawn up and placed in counting tubes, and placed in a gamma counter for the determination of the content of inorganic mercury that accumulated in them during the 48 hr subsequent to the administration of the dose of mercuric chloride. In a separate set of animals, the intrarenal distribution of inorganic mercury was determined 48 hr after the intravenous dose of mercuric chloride was asministered. Inorganic mercury accumulated mainly in the renal cortex and outer stripe of the outer medulla. In addition, the concentration of inorganic mercury in the outer stripe of the outer medulla was twice that in the cortex. The findings obtained with the isolated tubular segments revealed that most of the accumulated inorganic mercury in the kidneys of the rats was in the proximal tubule. The content of inorganic mercury in the proximal straight tubules was significantly greater than that in the proximal convoluted tubules. Negligible amounts of inorganic mercury were detected in the distal segments of the nephron and collecting duct. The data obtained from the isolated tubular segments indicate that the increased accumulation of inorganic mercury that occurs in the outer stripe of the outer medulla is due specifically to increased accumulation of inorganic mercury in the proximal straight tubules. The method used to study the accumulation of inorganic mercury in segments of the nephrons proves to be sensitive enough to explain the mechanism for various patterns of accumulation of inorganic mercury in the kidneys of rats.