boron and Atrophy

Carboranes are a class of carbon-containing polyhedral boron-cluster compounds with globular geometry and hydrophobic surface that interact with hormone receptors. Estrogen deficiency results in marked bone loss due to increased osteoclastic bone resorption in females, but estrogen replacement therapy is not generally used for postmenopausal osteoporosis due to the risk of uterine cancer. We synthesized a novel carborane compound BE360 to clarify its anti-osteoporosis activity. BE360 showed a high binding affinity to estrogen receptors (ER), ERalpha and ERbeta. In ovariectomized (OVX) mice, femoral bone volume was markedly reduced and BE360 dose-dependently restored bone loss in OVX mice. However, BE360 did not exhibit any estrogenic activity in the uterus. BE360 also restored bone loss in orchidectomized mice without androgenic action in the sex organs. Therefore, BE360 is a novel selective estrogen receptor modulator (SERM) that may offer a new therapy option for osteoporosis.

Topics: Animals; Atrophy; Bone and Bones; Bone Density; Boron; Boron Compounds; Drug Design; Estrogen Receptor Modulators; Female; Genitalia; Male; Mice; Uterus

Previous studies on the reproductive toxicity of boric acid have indicated that male rodents suffer testicular atrophy after treatment. There were, however, no studies of the potential effects on female fertility or on the neonate. In addition, no study described the development of the testicular lesion, thought to be related to the mechanism of toxicity. A Reproductive Assessment by Continuous Breeding (RACB) study using mice exposed to boric acid at 1000, 4500, and 9000 ppm in the diet indicated that there are probably multiple sites of action, although male fertility appears very sensitive. Possible effects on female fertility cannot be separated from potential developmental toxicity and need additional investigation. Decrements in sperm motility were observed at all exposure levels, and testicular atrophy was confirmed in high- and middle-dose-group males. This was investigated further by timed serial-sacrifice studies using 9000 ppm in the diet of rats, which found that the first lesion seen in the testis was an inhibition of spermiation (release of mature spermatids). With continued dosing, this was followed by a disorganization of the normal ordered layering of the seminiferous epithelium, germ cell sloughing and death, and finally, atrophy. Subsequent studies using additional doses (2000, 3000, 4500, 6000, and 9000 ppm) found that it was possible to observe inhibited spermiation that did not progress to atrophy (4500 ppm and below) within the 9-week exposure period.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Atrophy; Boric Acids; Boron; Dose-Response Relationship, Drug; Female; Fertility; Litter Size; Male; Mice; Pregnancy; Reproduction; Spermatogenesis; Testis

High-dose boric acid (BA) exposure produces testicular lesions in adult rats characterized by inhibited spermiation (IS) that may progress to atrophy. In vivo and in vitro studies addressed possible mechanisms. In vivo, boron tissue disposition was examined, since no detailed data existed, and relevant boron concentrations for in vitro studies needed to be set. Since BA induces riboflavinuria and also affects calcium/phosphorus homeostasis, and testis zinc appears essential for normal testis function, we examined BA effects on flavin status and testis levels of phosphorus (P), calcium (Ca) and zinc (Zn). Data showed that the testicular toxicity and central nervous system (CNS) hormonal effect were not due to selective boron accumulation in testis or brain/hypothalamus, with testis boron concentrations at approximately 1 to 2 mM; that riboflavin deficiency is not involved, due to both the absence of overt signs of deficiency and effects on tissue flavin content during BA exposure; and that changes in testis P, Ca and Zn levels did not precede atrophy, and are therefore unlikely to be mechanistically relevant. In vitro studies addressed the hallmarks of the BA testicular toxicity: the mild hormone effect, the initial IS, and atrophy. No effect of BA on the steroidogenic function of isolated Leydig cells was observed, supporting the contention of a CNS-mediated rather than a direct hormone effect. Since increased testicular cyclic adenosine monophosphate (cAMP) produces IS, and a role for the serine proteases plasminogen activators (PAs) in spermiation has been proposed, we examined in vitro BA effects on both Sertoli cell cAMP accumulation and PA activity, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Atrophy; Boric Acids; Boron; Cells, Cultured; Cyclic AMP; DNA Replication; Dose-Response Relationship, Drug; Male; Rats; Spermatogenesis; Testis; Testosterone; Tissue Distribution; Trace Elements