Quantification of testosterone and testosterone glucuronide in testicular and peripheral plasma of mature thorny skate ( Raja radiata)

Abstract

Testicular and peripheral blood was collected from mature male thorny skate ( Raja radiata). “Free” testosterone and testosterone released by β-glucuronidase were quantified using gas-liquid chromatography after prior purification by thin-layer and paper chromatography. The concentration of free testosterone was greater in the testicular than in the peripheral plasma, indicating that the testis is a site of testosterone secretion. In three of the five fish examined the concentration of testosterone glucuronide was higher in the testicular effluent plasma than in the peripheral plasma, indicating that in these fish testosterone glucuronide is a secretory product of the testis. In the two remaining fish the concentrations of testosterone glucuronide in the testicular effluent were similar or slightly lower than in peripheral plasma, thus suggesting that testosterone glucuronide is not being secreted by the testis in these fish.