A hypercholesterolemic diet fed to rats revealed significant interstrain differences in plasma cholesterol levels. Hyperresponding and hyporesponding strains could be distinguished from normoresponding strains within 3 weeks. The increase in plasma cholesterol level was more than 300 mg/100 ml in the hyperresponding strains BN/Cpb, SD/Cpb and WE/Z and less than 50 mg/100 ml in the hyporesponding strains S3/Cpb and SHR/Cpb. These differences were primarily genetically determined: the calculated coefficient of genetic determination (g2) of the response was 0.84. The response is not correlated with variation in plasma esterase or alkaline phosphatase isozyme patterns.

Nine inbred strains of the rat (Rattus norvegicus) were screened for differences in electrophoretically detectable proteins. Interstrain variation was observed for 7 of 26 proteins. Three of these variants have not been described previously: leucine aminopeptidase (Lap-1), major urinary protein (Mup-1), and seminal vesicle protein (Svp-2). Genetic analysis revealed two autosomal alleles for each of these polymorphisms. The loci Lap=1, Mup-1, and Svp-2 are linked neither to one another nor to the previously described Svp-1 and Es-4 loci. Each of the nine strains can be identified now by a specific set of monogenic markers.

No abstract

A fast-migrating F' zone of the prealbumin serum esterase system of rabbits is demonstrated in low frequency in the breed Vienna White (stock Cpb:VW). Evidence is given that this zone is controlled by a third allele of the Est-2 locus. The zymotypic expression of this allele (Est-2-F') shows codominance in combination with the Est-2-F allele and complete dominance in combination with the Est-2-F' allele. In contradistinction to the F zones of the Est-2-F allele, the F' zone possesses no atropinesterase activity.

Discontinuous starch gel electrophoresis revealed a fourth allele of rabbit pre-albumin serum esterase at locus Est-2. This allele is designated Est-2f and appears to be silent. In addition to the prealbumin serum esterases, another serum esterase system was studied in rabbits. This system is localized in the beta-globulin region. Genetic analysis indicated that one locus with two codominant alleles controls the variation in this region. Linkage of this system with Est-1 and Est-2 of the prealbumin serum esterases was demonstrated. Comparison of the arrangement of these esterase loci on linkage group VI with the esterase loci on chromosome 8 of the mouse gives additional support for the theory of evolutionary conservation of chromosomal segments coding for mammalian esterases.