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Updated: Sep 27, 2026
Transgenic Rodent Assay for Quantifying Male Germ Cell Mutant Frequency
Published on: August 6, 2014
Mouse bone marrow micronucleus test results do not predict the germ cell mutagenicity of N-hydroxymethylacrylamide in
Kristine L Witt1, Lori A Hughes, Leo T Burka
1Information Sciences Division, Integrated Laboratory Systems, Inc., Research Triangle Park, North Carolina, USA.
Abstract:
N-Hydroxymethylacrylamide (NHMA), a mouse carcinogen inactive in the Salmonella assay and mouse micronucleus (MN) assay, was tested for reproductive effects in a mouse continuous breeding study. In that study, increased embryonic deaths were observed after 13 weeks exposure of parental animals to NHMA via drinking water (highest dose, 360 ppm); the results indicated the possible induction of chromosome damage in germ cells of treated males. An additional mouse MN test was conducted using a 31-day treatment period to better match the dosing regimen used in the breeding study; the results were negative. Additional studies were conducted to explore the germ cell activity of NHMA. A male mouse dominant lethal study was conducted using a single intraperitoneal injection of 150 mg/kg NHMA; the results were negative. A follow-up study was conducted using fractionated dosing, 50 mg/kg/day for 5 days; again, no increase in dominant lethal mutations was observed. NHMA (180-720 ppm) was then administered to male mice in drinking water for 13 weeks, during which three sets of matings occurred. Two weeks after mating, females were killed and the uterine contents were analyzed. Large, dose-related increases in dominant lethal mutations were observed with increasing length of exposure. The magnitude of the increases stabilized after 8 weeks of treatment. However, the frequency of micronucleated peripheral blood erythrocytes was not elevated in mice treated for 13 weeks with NHMA in drinking water. Thus, NHMA appears to be unique in inducing genetic damage in germ cells but not somatic cells of male mice.
Insights
N-Hydroxymethylacrylamide (NHMA) caused reproductive harm and germ cell mutations in male mice, despite negative results in somatic cell tests. This chemical uniquely damages reproductive cells but not body cells.
Area of Science:
- Toxicology
- Reproductive Toxicology
- Genetics
Background:
- N-Hydroxymethylacrylamide (NHMA) is a known mouse carcinogen.
- NHMA showed negative results in standard Salmonella and mouse micronucleus (MN) assays.
- Previous studies indicated potential reproductive effects and germ cell damage.
Purpose of the Study:
- To investigate the reproductive toxicity of NHMA in a continuous breeding mouse study.
- To further explore the germ cell mutagenicity of NHMA.
- To compare germ cell and somatic cell genotoxicity of NHMA.
Main Methods:
- Continuous breeding study with male mice exposed to NHMA in drinking water.
- Dominant lethal assays with single and fractionated NHMA injections.
- Extended exposure dominant lethal assay with NHMA in drinking water.
- Micronucleus (MN) test on peripheral blood erythrocytes.
Main Results:
- Increased embryonic deaths observed in the continuous breeding study.
- Large, dose-related increases in dominant lethal mutations after prolonged NHMA exposure in male mice.
- Negative results in somatic cell MN tests, even after extended exposure.
- NHMA induced germ cell genetic damage but not somatic cell damage.
Conclusions:
- NHMA induces reproductive toxicity and germ cell mutations in male mice.
- NHMA exhibits a unique genotoxic profile, affecting germ cells but not somatic cells.
- Findings highlight the importance of germ cell-specific testing for reproductive toxicants.
