Morphometric and Functional Investigation on the Leydig Cells in Experimental Unilateral Cryptorchism in the Rat

By distal gubernaculotomy on one side in newborn rats testicular descent was prevented on that side, and unilateral cryptorchid rats were obtained. Leydig cell structure and function was studied at 20, 30 and 100 days of age, using both morphometric and biochemical techniques. Up to 30 days of age no differences in structure of the interstitium and Leydig cells, or testicular testosterone concentration were observed between the scrotal and the abdominal testicles. In contrast the tubular cells in the abdominal testicle were highly damaged already at 30 days of age. The abdominal testicles of the 100‐day‐old rats contained the same total number of Leydig cells as the scrotal testicles, but the size of these cells, and the testicular testosterone concentration were highly reduced. Thus Leydig cell function in the cryptorchid testicle was maintained at 30 days but highly impaired at 100 days of age. Tubular damage occurred prior to the Leydig cell malfunction.