Meeting Abstract
Steroid hormones often travel in circulation as inactive sulfated forms. For example, estrone sulfate and dehydroepiandrosterone sulfate are abundant in human plasma. The enzyme steroid sulfatase (STS) acts to remove the sulfate group, generating active hormones. The role of STS is presumably to provide active steroids to local tissues; however, little is known about which tissues are the major sites of STS activity. This information has implications for understanding steroid hormone physiology and pathology. This study investigated the tissue distribution of STS in two laboratory models, the house mouse, Mus musculus and the African clawed frog, Xenopus laevis. Tissues included were: heart, liver, small intestine, skeletal muscle and gonads of both genders. An 3H-estrone conversion assay was used to measure STS activity in microsomes and cytosols. In the mouse, liver STS activities were highest for both genders. Testis STS levels were slightly below liver, while ovary, small intestine, heart and muscle STS activities were even lower. For the frog, testis STS activity was highest, with small intestine lower, followed by liver, heart and muscle, respectively. We validated the enzyme activity assay by using two specific STS inhibitors, EMATE and 667 Coumate. Both compounds eliminated STS activity in liver microsomes and cytosols of both species. Liver and testis microsomes of both species had Km values in the reported range for STS. The tissue distributions for STS differ somewhat from those reported for humans. The high values for testis STS in both mice and frogs suggests a potential role for sulfated steroids in testicular steroidogenesis.
