EXCRETION OF STEROID HORMONES IN RODENTS: ...

BUSSO JM; RUIZ RD

Contemporary aspects of endocrinology

Intech Open Acces Publisher

Año: 2011; p. 375 - 396

Steroid hormones are dissociated from their receptors and metabolized by the target cell or the liver, both of which possess enzymes capable of altering the specific steroids and rendering them biologically inactive and water soluble. Typically, the synthesis of steroid metabolites involves reduction or removal of side chain or attached groups or both, as well as the combination with other molecules (conjugation) such as glucose to form a glucuronide or conjugation with sulfate. The relative emphasis on sulfate or glucuronide varies with the steroid and/or species. Similarly, in the last years several reports on steroid radiometabolism contributed to enhance our knowledge and support premise that different steroids also show species differences and are excreted to different extents in urine and feces, and that the same steroid is excreted to different extents in urine and feces of different species. Steroid receptors and the co-evolution of steroidogenic enzymes as well as steroid-inactivating enzymes had an important role in the evolution of complex regulatory networks in vertebrates, contributing to vertebrate survival and diversification in the last 500 million years. For more than 25 years independent laboratories have pioneered techniques for measuring hormonal patterns in voided urine and feces. Excreted urinary or fecal hormone metabolites accurately reflect hormonal patterns in blood with the appropriate delay in passage from the blood into excreta. Whether the hormone is primarily passed into urine or feces is also species-dependent, and this information is useful to a subsequent precise monitoring of hormone variation because metabolite concentrations are frequently 2 to 4 times higher than the concentration of the parent steroid in blood. Studies on steroid excretion in rodents have neglected the vast biodiversity of this group, which comprises more than 2000 species of mammals and encompasses a staggering diversity of form, behavior and physiology. Rodents are not regarded as threatened mammals, and public appreciation about their biological importance is scarce and tends to overlook the ecological role and conservation problems of an order representing about 41% of mammalian species. Moreover, scientists have frequently employed several rodent species for research purposes, and have even used rodents as animal models for biomedical studies. Therefore, because of species-specific differences at different anatomical and physiological levels in steroid metabolism, detected even in closely related species, scientific information on the route of excretion is essential to support validations steps (such as steroid extraction efficiency control) and hormone monitoring strategies (such as which matrix will be used for hormone determination).  Based on updated endocrinological data obtained by noninvasive hormone monitoring application in wild, laboratory and farmed rodents, in this chapter we develop a hypothesis-driven revision about comparative endocrine analysis of the routes of gonadal and adrenocortical steroid excretion, beginning with sex steroids in chinchilla. Domesticated Chinchilla (Chinchilla lanigera), as an animal model of their endangered counterparts, was subjected to radiometabolism studies of progesterone, corticosterone, testosterone and estradiol in our laboratory. A preferential route of steroid metabolite excretion has been postulated in rodents: in Hystrichomorpha, the urinary route is preferential whereas in Sciumorpha and Myormorpha, the primary excretory route is the feces. The present compilation of radio-infusion available studies in rodent  will be useful to generate a comparative endocrine database; it will hopefully help interested people to enhance their understanding about a non-invasive strategy to monitor the endocrine status of an animal, and it will provide them with some research guidelines for application.