Normative reproductive indices for male and female adult Sprague-Dawley rats

doi:10.1016/S0010-7824(99)00017-7

Contraception

Volume 59, Issue 3, March 1999, Pages 203-207

https://doi.org/10.1016/S0010-7824(99)00017-7 Get rights and content

Abstract

The Sprague-Dawley rat is traditionally used as the experimental model for the study of contraceptive agents and reproductive toxicants. Until recently, the normative values used to compare hormone levels after drug exposure were based on the values generated by radioimmunoassay methods developed 30 years ago. To ascertain normative reproductive indices for adult female and male Sprague-Dawley rats over a 6-month age period, we measured luteinizing hormone, testosterone, and estradiol using commercially available kits that employ updated assay techniques. In addition, sperm indices were correlated with reproductive hormones over the same time period. Animals were killed at 107, 128, 156, 212, and 268 days of age irrespective (for females) of cycle stage. Serum LH levels did not change with increasing age; however, the female rats had significantly higher LH values than did the males at comparable ages (p < 0.001). Testosterone levels and sperm parameters did not significantly change with increasing age. Estradiol levels were significantly higher in 107-day-old female rats than they were in female rats in all older age groups (p < 0.01). The values reported can be used in designing and interpreting data generated in ongoing, long term toxicological and contraceptive studies using the rat animal model.

Introduction

The Sprague-Dawley rat traditionally is used as the experimental model for the study of contraceptive agents and reproductive toxicants. The rat grows rapidly, reproduces frequently, and is inexpensive. Evaluating changes in reproductive hormone levels and sperm concentration can provide useful information about effects of administered agents on the reproductive axis. Until recently, the normative values used to compare hormone levels after drug exposure were based on the values generated by radioimmunoassay methods developed >30 years ago.1, 2, 3, 4 Recently, to improve the ability to measure low levels of serum hormones, novel assay methods using monoclonal antibodies and the immunometric assay principle were applied to the measurement of hormone values. A highly sensitive immunofluorometric assay for rat LH improves the sensitivity and accuracy of measuring low LH concentrations in small sample volumes.5 Similarly, assays for measuring steroids also were improved and simplified.6, 7, 8, 9 To ascertain normative reproductive indices for adult female and male Sprague-Dawley rats, we measured serum luteinizing hormone (LH), testosterone (T), and estradiol (E₂) using commercially available kits that employ updated assay techniques. In addition, sperm indices were correlated with reproductive hormones over the same period.

Section snippets

Animals

Adult male and female Sprague-Dawley rats, age 92 days on arrival, were purchased from the Charles River Laboratories (Portage, MI), and housed at ROW Laboratories (Gaithersburg, MD) for 8 days before random distribution into study groups of 12–16 rats. The animals were housed under controlled light (12-h bright/12-h dark cycle) and temperature conditions in polycarbonate cages suspended on stainless steel racks. The cages were equipped with filter paper liners and contained Beta chip,

Animals

The animals gained weight throughout the study period (Table 1). There was no period of weight reduction in the course of this study

Sperm parameters

The numbers of epididymal sperm and testicular spermatids did not differ significantly across the period studied (Table 2 ). The sperm motion parameters did not differ significantly across this period (Table 2).

Hormone assays

The sensitivity and precision of each hormone assay were determined. Sensitivity of the rat LH assay was 0.03 ng/mL, and the intra- and interassay

Discussion

Unlike previous studies which grouped together adult male rats between the ages of 3 and 6 months,14, 15, 16, 17 the present study reports a monthly evaluation of hormone levels throughout the 3–9-month age period. Comparisons between animals ranging in age from 107 to 268 days indicate no significant changes occur in LH levels during that time. There does appear to be a gradual reduction in steroid levels in the same period. However, the semen parameters did not change during the period

Acknowledgements

The authors thank Reina Lopez for manuscript preparation and Natasha Fung for assistance with data analysis.

References (22)

R. Ghanadian et al.
Serum testosterone and dihydrotestosterone changes with age in rat
Steroids
(1975)
V.L. Gay et al.
Patterns of gonadotrophin secretion associated with ovulation
Fed Proc
(1970)
G.D. Niswender et al.
Radioimmunoassay for rat luteinizing hormone with antiovine LH serum and ovine LH-131I
Proc Soc Exp Biol Med
(1968)
A.R. Midgley et al.
Radioimmunoassay of steroids
Acta Endocrinologica
(1970)
R.S. Swerdloff et al.
Serum LH and FSH during sexual maturation in the male rateffect of castration and cryptorchidism
Endocrinology
(1971)
A.M. Haavisto et al.
A supersensitive immunofluorometric assay for rat luteinizing hormone
Endocrinology
(1993)
J.J. Bonavera et al.
In the male Brown-Norway (BN) male rat, reproductive aging is associated with decreased LH-pulse amplitude and area
J Androl
(1997)
A.E. Karpas et al.
Diminished luteinizing hormone pulse frequency and amplitude with aging in the male rat
Endocrinology
(1983)
Coat-A-Count Total Testosterone Veterinary Application. Diagnostics Products Corporation (DPC), Los Angeles, CA 1992,...
125I-Estradiol, Pantex Catalogue #047, Santa Monica, CA 1995,...

R.P. Amann et al.

The male rabbit. III. Determination of daily sperm production by means of testicular homogenates

J Animal Sci

(1969)

Cited by (22)

Paternal factors in neurodevelopmental toxicology: THC exposure of male rats causes long-lasting neurobehavioral effects in their offspring
2020, NeuroToxicology
Citation Excerpt :
Then we assessed the effects of this exposure on reproduction and neurobehavioral development of the offspring. A duration of 28 days was used to extend exposure into the second sperm cycle of Sprague-Dawley rats, which are commonly used to explore the effects of reproductive toxins (Sokol et al., 1999). Behavioral function was measured in a test battery including tests of locomotor activity, emotional function and cognition.
The potential health risks of cannabis are of growing concern, including effects on reproduction and development. Extensive research has investigated risks associated with maternal exposure to THC during gestation and its impacts on the development of offspring, but little research has been done regarding paternal THC exposure effects prior to conception. We have previously found that paternal THC exposure in rats causes changes in sperm methylation. In an initial study we also showed that a 12-day paternal THC exposure prior to conception alters locomotor activity and impairs cognitive function of their offspring. This study investigated the cross-generational effects of chronic paternal THC exposure in rats (0, 2, or 4 mg/kg/day SC for 28 days) prior to mating with drug naïve females. The offspring of THC-exposed male rats had significant alterations in locomotor activity and cognitive function. Specifically, during adolescence there was significant locomotor hyperactivity in the offspring of males exposed to 2 mg/kg/day of THC. During the novel object recognition task, the controls maintained their relative preference for the novel object across the duration of the ten-min session while the rats whose fathers received THC (2 mg/kg/day) showed a significantly greater drop-off in interest in the novel object during the second half of the session. Learning in the radial-arm maze was significantly delayed in the offspring of males exposed to 4 mg/kg/day of THC. This study shows that premating chronic paternal THC exposure at multiple dose regimens can cause long-lasting detrimental behavioral effects in their offspring, including abnormal locomotor activity and impaired cognitive function. Future studies should investigate the underlying mechanisms driving these aberrant developmental outcomes and seek to identify possible treatments of alleviation in the presence of paternal THC exposure.
Sex differences in the fetal programming of hypertension
2008, Gender Medicine
Background: Numerous clinical and experimental studies support the hypothesis that the intrauterine environment is an important determinant of cardiovascular disease and hypertension.
Objective: This review examined the mechanisms linking an adverse fetal environment and increased risk for chronic disease in adulthood with an emphasis on gender differences and the role of sex hormones in mediating sexual dimorphism in response to a suboptimal fetal environment.
Methods: This review focuses on current findings from the PubMed database regarding animal models of fetal programming of hypertension, sex differences in phenotypic outcomes, and potential mechanisms in offspring of mothers exposed to an adverse insult during gestation. For the years 1988 to 2007, the database was searched using the following terms: fetal programming, intrauterine growth restriction, low birth weight, sex differences, estradiol, testosterone, high blood pressure, and hypertension.
Results: The mechanisms involved in the fetal programming of adult disease are multifactorial and include alterations in the regulatory systems affecting the long-tterm control of arterial pressure. Sex differences have been observed in animal models of fetal programming, and recent studies suggest that sex hormones may modulate activity of regulatory systems, leading to a lower incidence of hypertension and vascular dysfunction in females compared with males.
Conclusions: Animal models of fetal programming provide critical support for the inverse relationship between birth weight and blood pressure. Experimental models demonstrate that sex differences are observed in the pathophysiologic response to an adverse fetal environment. A role for sex hormone involvement is strongly suggested,with modulation of the renin-angiotensin system as a possible mechanism.
Properties of in situ gelling nasal inserts containing estradiol/methyl β-cyclodextrin
2004, Journal of Drug Delivery Science and Technology
The purpose of the study was to incorporate estradiol into in situ gelling nasal inserts by complexation with methyl-β-cyclodextrin (MβCD) and to evaluate the in vivo performance of estradiol-loaded inserts, solutions, and microparticles in rats. Aqueous solutions of estradiol/MβCD complexes and hydrophilic polymers (carrageenan, sodium alginate, HPMC, PVP 90, and xanthan gum) were freeze-dried to form solid, sponge-like nasal inserts. The drug release, water and moisture uptake, and bioadhesion potential of inserts were investigated. The inserts were administered nasally to male rats and the serum estradiol level was followed for 6 h by RIA. The addition of MβCD to carrageenan solutions increased the viscosity significantly, which could be explained by the dehydration of carrageenan, the addition of cations as impurities in MβCD, and interactions between carrageenan and MβCD. The bioadhesion potential of HPMC K15M was reduced by the addition of MβCD. The water uptake of carrageenan inserts was not influenced while the moisture sorption was enhanced due to the hygroscopicity of MβCD. The release of the drug complex from inserts was as follows: HPMC E5 > PVP 90 > sodium alginate > xanthan gum > carrageenan. Neither the estradiol dose nor the complex molar ratio had an effect on the drug release from inserts. In vivo estradiol levels after nasal application of an aqueous solution (Aerodiol) and microparticles resulted in high peaks (approx. 0.42-0.47 pg/ml/g/μg) with short t_max. Carrageenan microparticles showed a delayed serum peak level compared to PVP 90 (t_max : 30 and 10 min, respectively), both reached 80-90% relative bioavailability. Nasal inserts led to a more gradual absorption of estradiol with lower peak serum levels (0.13-0.14 pg/ml/g/μg). Gelled carrageenan inserts were still present in the nasal cavity 6 h post-administration. The relative bioavailability of carrageenan inserts was slightly higher than for PVP 90 (49 vs. 40%).
Some aspects relating to the evaluation of the effects of chemicals on male fertility
2003, Regulatory Toxicology and Pharmacology
Reviews and studies on individual compounds were analyzed as to the suitability of different study designs and endpoints for detecting adverse effects of chemicals on male reproduction in animal species. Of the endpoints investigated, the most sensitive proved to be histopathology of the testes. Using refined histopathology, effects could be detected with a high degree of sensitivity as early as 4 weeks after treatment. Other sensitive endpoints were the weights of reproductive organs, including accessory glands, i.e., testis, epididymis, prostate, and of the seminal vesicle, as well as sperm parameters such as sperm count, sperm morphology, and sperm motility. Sperm motility was found to be in some cases more sensitive than histopathology. The above parameters showed a higher sensitivity than fertility parameters. In fact, in most cases, not only one but several endpoints were affected. Continuous breeding studies and 90-day studies with additional measurements of sperm parameters were similarly effective in detecting compounds which affect male fertility. Interspecies extrapolation factors (IEFs) have been derived for the most sensitive endpoints in laboratory animals. If the calculation is based on caloric demand and a sensitive endpoint of reproductive toxicity, many IEFs tend to be about 1, indicating that humans are generally not more susceptible to reproductive toxicants than laboratory animals. With respect to hazard identification, it is possible to detect adverse effects on male reproduction in a standard subacute study with concentrations that produce significant general toxicity. If effects are found, for the risk assessment the NOAEL has to be determined by testing specific sensitive parameters as specified above.
Protein restriction during pregnancy induces hypertension in adult female rat offspring - Influence of oestradiol
2012, British Journal of Nutrition
Periconceptional alcohol alters in vivo heart function in ageing female rat offspring: Possible involvement of oestrogen receptor signalling
2023, Experimental Physiology

View all citing articles on Scopus

View full text

Original Research ArticlesNormative reproductive indices for male and female adult Sprague-Dawley rats

Abstract

Introduction

Section snippets

Animals

Animals

Sperm parameters

Hormone assays

Discussion

Acknowledgements

Steroids

Patterns of gonadotrophin secretion associated with ovulation

Fed Proc

Radioimmunoassay for rat luteinizing hormone with antiovine LH serum and ovine LH-131I

Proc Soc Exp Biol Med

Radioimmunoassay of steroids

Acta Endocrinologica

Serum LH and FSH during sexual maturation in the male rateffect of castration and cryptorchidism

Endocrinology

A supersensitive immunofluorometric assay for rat luteinizing hormone

Endocrinology

In the male Brown-Norway (BN) male rat, reproductive aging is associated with decreased LH-pulse amplitude and area

J Androl

Diminished luteinizing hormone pulse frequency and amplitude with aging in the male rat

Endocrinology

The male rabbit. III. Determination of daily sperm production by means of testicular homogenates

J Animal Sci

Original Research Articles
Normative reproductive indices for male and female adult Sprague-Dawley rats