Thyroid hormone beta receptor activation has additive cholesterol lowering activity in combination with atorvastatin in rabbits, dogs and monkeys.

BACKGROUND AND PURPOSE: Thyroid hormone receptor (TR) agonists are in clinical trials for the treatment of hypercholesterolaemia. As statins are the standard of clinical care, any new therapies must have adjunctive activity, when given in combination with statins. As already known for the statins, the cholesterol lowering effect of TR activation involves increased expression of the low-density lipoprotein receptor. Using animal models, we tested whether TR activation would have additive cholesterol lowering activity in the presence of effective doses of a statin. EXPERIMENTAL APPROACH: We evaluated the activity of a liver-targeted prodrug, MB07811, of a novel TH receptor beta agonist, MB07344, as monotherapy and in combination with atorvastatin in rabbits, dogs and monkeys. KEY RESULTS: In rabbits, MB07344 (i.v.) decreased total plasma cholesterol (TPC) comparable to that achieved with a maximally effective dose of atorvastatin (p.o.). The addition of MB07344 to atorvastatin resulted in a further decrease in TPC. Similarly, the addition of MB07811 (p.o.) to atorvastatin treatment decreased TPC beyond the level achieved with either agent as monotherapy. In dogs and monkeys, atorvastatin and MB07811 were administered as monotherapy or in combination. Consistent with the rabbit studies, the combination treatment caused a greater decrease in TPC than either MB07811 or atorvastatin administered as monotherapy. CONCLUSIONS AND IMPLICATIONS: We conclude that the effects of MB07811 and atorvastatin in lowering cholesterol are additive in animals. These results would encourage and support the demonstration of similarly improved efficacy of combination versus monotherapy with such agents in the clinic.

Effect of hypophysectomy, sex of host, and/or number of transplanted testes on Sertoli cell number and testicular size of syngeneic testicular grafts in Fischer rats.

One or more neonatal testicular grafts were transplanted for 60-65 days into young adult inbred Fischer rats to determine the effect of hypophysectomy, sex of host, and/or the number of transplanted testes on testicular size and Sertoli cell number. All host rats had been castrated or ovariectomized and some were hypophysectomized as well. At the end of the treatment, testes were fixed and embedded in Epon before histologic sections (0.5 micrometer or 20 micrometers) were evaluated by stereology. Testicular grafts placed in castrated adult male rats with intact pituitaries weighed more (p < 0.01) and had more (p < 0.01) Sertoli cells than those placed in hypophysectomized hosts. Testicular grafts that were recovered from hypophysectomized rats 34 days posttransplantation and placed in pituitary-intact males for 30 day had larger (p < 0.05) parenchymal weights and more Sertoli cells than did testes re-transplanted into hypophysectomized rats. However, this delayed period of Sertoli cell proliferation id not extend to 65 days of hypophysectomy. When two or four testes were transplanted into castrated males or ovariectomized female hosts for 65 days, there was no difference in the graft weights or Sertoli cell numbers between sexes. Four transplanted testes per rat produced more (p < 0.01) total testicular parenchyma and a greater (p < 0.01) number of Sertoli cells per testis than did two tests regardless of sex of the host. This model has shown that the period of Sertoli cell proliferation can be delayed by hypophysectomy, that Sertoli cell number can be influenced by endogenous hormones, and that a major component in regulation of testicular size is at the level of the testis in this model. Hence, this model should facilitate study of experimental endocrine manipulation control and potential experimental intervention to increase Sertoli cell number and testicular size.

Human chorionic gonadotropin protects Leydig cell function against 2,3,7,8-tetrachlorodibenzo-p-dioxin in adult rats: role of Leydig cell cytoplasmic volume.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) alters testicular steroidogenesis and reduces Leydig cell volume and number; however, human chorionic gonadotropin (hCG) stimulates testosterone production, increases the number and volume of Leydig cells and prevents TCDD's inhibition of testosterone production. The objective of this study was to determine if hCG protects Leydig cell function by maintaining sufficient Leydig cell cytoplasmic volume in TCDD-treated rats. Adult, male Sprague Dawley rats were divided into six treatment groups. Half of the animals received TCDD in corn oil (50 micrograms/kg body wt) and half received corn oil alone on Day 7 only. Additionally the rats received daily treatment of saline for 14 days, saline for 7 days and then hCG for 7 days, or hCG for 14 days. Rats were sacrificed on Day 14 and tissues collected. The decapsulated left testes were incubated in Eagles MEM for 2 h to determine basal production of testosterone and for 2 additional hours after the addition of hCG (100 IU) to the culture media. The right testis was evaluated by stereology to determine the volume of Leydig cells. Body weight was reduced (P < 0.01) in each TCDD-treated group; whereas, testicular weight was not affected by TCDD or hCG treatment. hCG prevented the TCDD-induced reduction in prostate and seminal vesicles weights. TCDD reduced the total volume of Leydig cell cytoplasm in saline-treated rats, but hCG eliminated the TCDD-induced reduction in Leydig cell cytoplasmic volume. hCG prevented the TCDD-induced reduction in Leydig cell function for both the 7- and 14-day treatments. Variation in the total volume of Leydig cell cytoplasm induced by the various treatment combinations was positively correlated with stimulated testosterone production in vitro (r = 0.486; P < 0.01) and the weight of the androgen sensitive organs (seminal vesicles, r = 0.562, P < 0.01; prostate, r = 0.380, P < 0.05). These data support the hypothesis that hCG prevents the TCDD-reduced Leydig cell function by maintaining sufficient Leydig cell cytoplasm and organelle content.

2,3,7,8-Tetrachlorodibenzo-p-dioxin reduces the number, size, and organelle content of Leydig cells in adult rat testes.

Exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) alters testicular steroidogenesis and reduces total Leydig cell volume in the testis. However, its effect on Leydig cell number, size, and organelle content had not been determined in adult rats. Adult male rats received a single intraperitoneal injection of TCDD at a dose of 0, 12.5, 25.0, or 50.0 micrograms/kg body weight. Testicular tissues were obtained from rats 4 weeks after treatment. Testes were vascularly perfused with glutaraldehyde, embedded in Epon 812, sectioned at 0.5 micron, stained with toluidine blue, and evaluated by stereology for number and size of Leydig cells. Specimens from control and high dose groups were prepared for electron microscopy to quantify Leydig cell organelle content. TCDD treatment reduced (P < 0.01) body weight in a dose-dependent fashion. Testicular weight was not significantly reduced by TCDD treatment. The volume of Leydig cell cytoplasm per testis was reduced (P < 0.01) four weeks after treatment. Reduction in total Leydig cell volume resulted from a reduced (P < 0.05) number of Leydig cells and a reduced (P < 0.01) size of individual Leydig cells. However, the volume density (percentage) of Leydig cells occupied by specific organelles was not influenced by TCDD treatment. As a result of reduced total Leydig cell volume with no change in volume density of organelles in Leydig cells, the volumes per testis of smooth endoplasmic reticulum and mitochondria were reduced (P < 0.01) by TCDD treatment. In conclusion, the TCDD-induced reduction in Leydig cell volume per testis is explained by reduced number and size of individual Leydig cells and resulted in a significant reduction in total volume of both Leydig cell smooth endoplasmic reticulum and mitochondria per testis. Reduction in content of organelles that are responsible for various key steps in steroidogenesis, could explain TCDD-reduced production of testosterone in rats.

XX sex reversal in a llama.

A 5-month-old llama was examined for evaluation of sexually ambiguous external genitalia. To determine the phenotypic, chromosomal, and gonadal sex of the llama, transrectal palpation and ultrasonography, contrast cystography, karyotype evaluation, laparoscopy, and necropsy were performed. A karyotype of 74,XX and finding of components of the müllerian duct system were suggestive of a female phenotype and chromosomal sex. On histologic evaluation, however, components of the wolffian duct system also were found, and the gonads were composed entirely of testicular tissue. The diagnosis was XX sex reversal, with a XX male phenotype.

Capacitation-like membrane changes and prolonged viability in vitro of equine spermatozoa cultured with uterine tube epithelial cells.

Reliable capacitation of equine spermatozoa has been a major obstacle in the development of equine in vitro fertilization. Experiments were done to compare in vitro capacitation of equine spermatozoa by use of heparin/caffeine, calcium ionophore, uterine tube epithelial cell (UTEC)-conditioned medium, and direct culturing of spermatozoa with UTEC (coculturing). Capacitation-like changes, as determined by chlortetracycline membrane staining patterns, developed with UTEC-conditioned medium and coculturing, equivalent to that with calcium ionophore. Both of these treatments induced more (P < 0.05) capacitation-like changes than did the control, a modified Tyrode's medium. More (P < 0.05) spermatozoa were viable after 24 hours of UTEC coculturing than in the control incubation.