Novel Testicular Products of the Human SHBG/ABP Gene
The blood of most mammalian species contains a binding protein for the sex-steroid hormones; in humans, this protein is most often referred to as sex-hormone binding globulin (SHBG). Rodents are notable exceptions to this rule, and it is well known that adult rats lack a plasma equivalent of SHBG. A similar protein has, however, been found in fetal rat blood during late gestation and is probably produced by the liver (1). In humans and other primates, the protein exhibits a high affinity for both androgens and estrogens (2), and plasma concentrations of SHBG determine the distribution of these hormones between the various protein-bound and nonprotein-bound fractions in the blood (3). As a result, SHBG influences the bioavailability of sex steroids at the target cell level (4). More recently, evidence has accumulated to support the concept that SHBG may play a more direct role in the actions of sex steroids, and a plasma membrane receptor that interacts specifically with SHBG has been isolated from human prostate tissue (5). This has resulted in a reevaluation of the physiological role of SHBG in a recent comprehensive review of the subject (6).
KeywordsAndrogen Binding Protein Human Testis cDNA Library Testicular Product Human Prostate Tumor Cell Line Target Cell Level
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