Fertilizing ability of spermatozoa from aged C57BL/6NNia mice

Spermatozoa from C57BL/6NNia mice (7- and 25-month-old males that produced offspring and 25-month-old males incapable of producing offspring which either mated or did not mate after being paired for 1 month with proven-fertile females) were tested in in-vitro fertilization studies. The 7-month-old males fertilized the largest number of oocytes (80-86%) in vitro and 79% of them subsequently developed into blastocysts in culture. Aged males which failed to mate fertilized the lowest number of oocytes (11-19%) with 48% developing to blastocysts. This group of mice had the lowest number of spermatozoa in the cauda epididymidis (3.2 +/- 0.4 x 10(5)/mg tissue) with fewer motile spermatozoa (22.3 +/- 5.1%) than younger males. The percentage of spermatozoa retaining their acrosome after 3 h in culture was higher in aged males which had not mated when compared to younger males that had mated. After 4 h in culture, however, the number of spermatozoa that had lost their acrosome was almost identical in the two groups. Superovulated mice which were artificially inseminated with spermatozoa from 25-month-old mice that had not mated did not become pregnant. Testosterone concentrations were lowest in aged mice not mating. These concentrations may explain the poor behavioural response of these males, but whether they account for the inability of spermatozoa to fertilize ova in vitro or in vivo after artificial insemination is not known.     

Autoregulation of testicular luteinizing hormone receptors in hypogonadal (hpg/hpg) mice

The autoregulation of testicular luteinizing hormone (LH) receptors was studied in hypogonadal (hpg/hpg) and normal mice. The basal concentration of LH receptors was more than three-fold higher in hpg/hpg than in normal mice. After injection of hCG, hpg/hpg mice showed a decrease in LH receptor levels which was not observed in normal mice. Plasma testosterone was undetectable in hpg/hpg mice, even after treatment with a single dose of hCG. Plasma prolactin levels were higher in hpg/hpg than in normal mice. The increase in basal LH receptor levels is thought to be due to a compensatory mechanism in which elevated prolactin could play a role. The differences between hpg/hpg and normal mice in the autoregulation of LH receptors observed could be due to the hypersensitivity of the physiologically immature testis in hpg/hpg mice to the action of hCG, to gonadotropin deficiency, particularly during the earlier stages of development, or to a direct effect of the hpg locus on the metabolism of LH receptors.These studies were supported by NIH Grants HD 12642 and HD 12671 (AB) and Grant CA-24145 (WGB).     

Differential effects of two alleles of the dy locus on the pituitary-testicular axis of mice.

Testicular function was studied in vivo and in vitro in adult male dy/dy and dy2J/dy2J dystrophic mice. The results demonstrate that testicular function in dy/dy mice is more affected. The basal levels of pituitary hormones measured were normal in dystrophic mice, except for the presence of hyperprolactinemia in dy/dy mice. In dy/dy mice testicular weight was diminished and a deficient transduction of the gonadotropic signal is present in vivo, accompanied by reduced efficiency of 17-hydroxylase and 17-hydroxysteroid dehydrogenase. In dy2J/dy2J mice the signal transduction is normal and the reduction in enzyme efficiency is limited to 17-hydroxysteroid dehydrogenase. The in vitro HCG-induced increases in production of testosterone (T) and estradiol (E2) were reduced in dy/dy/mice, and the data indicate a reduction of enzyme activity rather than in efficiency. In dy21/dy21/mice, HCG-induced T synthesis was increased, HCG-induced E2 synthesis was normal, but basal media E2 levels were reduced, with the in vitro efficiency of aromatase being suppressed under both basal and HCG-stimulated conditions, when compared to their normal littermates.     

Lithium-induced changes in the plasma and pituitary levels of luteinizing hormone,follicle stimulating hormone and prolactin in rats

Adult male Sprague-Dawley rats, maintained under a controlled photoperiod of LD 14:10 (white lights on at 06:00 h, CST), were injected with lithium chloride and changes in the levels of plasma and pituitary homogenates of luteinizing hormone (LH), follicle-stimulating hormone (FSH) and prolactin (PRL) were examined to evaluate the effects of this anti-manic drug on reproductive function. Two groups of rats were injected with lithium chloride intraperitoneally, twice daily at 09:00 and 16:00 h, for 2 and 7 days at a dosage of 2.5 meg/Kg body weight. Plasma and pituitary levels of LH, FSH and PRL were measured by radioimmunoassay. Plasma levels of LH were significantly (P<0.05) increased after 2 days of lithium treatment. In contrast, a significant (P<0.005) reduction in plasma levels of LH was evident when lithium injections were continued for 7 days. The plasma levels of FSH remained unaffected by lithium treatment by either time period. Lithium administered for 2 days did not bring about any significant alteration in the plasma levels of PRL, although there was a significant (P<0.002) reduction in plasma PRL levels after 7 days treatment. The concentrations of pituitary LH, FSH and PRL remained unchanged after 2 and 7 days of lithium treatment.     

Fertilization of Chinese hamster ova in vitro and in vivo and their subsequent development in culture

Oocytes from superovulated Chinese hamsters can be fertilized in vitro using the culture medium BWW (70% of 112 ova) or a modified BWW designated as MBWW (76% of 122 ova) when either medium is supplemented with 4 mg/ml of bovine serum albumin. Ova fertilized in vitro will also cleave to the 2-cell stage in either medium (52% in BWW, 87% in MBWW), but fail to develop any further in culture. Oocytes fertilized in vivo and recovered at the late 2-cell or early 4-cell stages from females on Day 3 of pregnancy have the capacity to develop into expanded blastocysts in MBWW. When early embryos that developed into morulae and early blastocyts in culture were transferred to surrogate females, eight normal young were born.     

Lithium: Short-term and chronic effects on plasma testosterone and luteinizing hormone concentrations in mice

The effects of short-term and chronic lithium administration on the concentrations of plasma testosterone (T) and luteinizing hormone (LH) were evaluated in C57BL/6 mice, maintained on a fixed photo-period of LD 14:10 (white lights on at 06:00 h, CST). Lithium chloride was injected intraperitoneally twice daily (at 09:00 and 16:00 h) in groups of adult male mice at a dosage of 2.5 meq/kg for 7 days, and 1.25 meq/kg for 21 days. Circulating levels of T and LH were measured by standard radioimmunoassay (RIA) methods. Plasma T levels showed a significant increase in mice treated with lithium for 7 days as compared to those in saline-injected control animals. However, there was no significant difference in the concentrations of plasma T between chronic (21 days) lithium-treated mice and the matched control. Plasma LH levels remained unchanged following both short-term and chronic lithium treatment.     

Infertility in transgenic female mice with human growth hormone expression: evidence for luteal failure

Introduction of the human growth hormone (hGH) gene fused with mouse metallothionein I promoter into domestic mice leads to ectopic synthesis of hGH, marked stimulation of somatic growth, and female sterility. Transgenic females (produced by mating transgenic males to normal females) mated but failed to become pregnant or pseudopregnant as evidenced by the recurrence of vaginal plugs every 5-7 days. Daily injections of 1 mg progesterone, starting on day 1 postcoitum (p.c.), maintained pregnancy, suggesting that the sterility of these animals is due to inadequate luteal function. In ovariectomized female transgenic mice, median eminence (ME) turnover of dopamine (DA) was increased, and plasma prolactin (PRL) levels were reduced, presumably because of the known lactogenic activity of hGH in rodents. From these observations we suspected that either 1) the corpora lutea of these animals are unresponsive to lactogenic hormones, or 2) hGH by stimulating tuberoinfundibular dopaminergic (TIDA) neurons interferes with the increase in PRL release that normally follows mating and this, in turn, leads to luteal failure. To distinguish between these possibilities, transgenic females were treated with PRL-secreting ectopic pituitary transplants from normal females of the same strain on day 1 p.c. Eight of ten treated females became pregnant and delivered litters. We conclude that infertility of transgenic female mice with hGH expression is due to activation of the TIDA system, suppression of endogenous PRL release, and luteal deficiency.