New polymorphisms of esterase 7 and esterase 8 in inbred strains of rats: tissue expression and linkage studies.

Two new esterase polymorphisms (Es-7 and Es-8) were identified in the testis homogenate of laboratory rats, Rattus norvegicus, by using discontinuous gradient polyacrylamide gel electrophoresis. Es-7 expressed two phenotypes: ES-7A (fast) and ES-7B (slow). Es-8, which migrated in the cathodal region rather than the ES-7 region, also expressed two phenotypes: ES-8A (fast) and ES-8B (slow). Linkage tests among Es-2, Es-7, and Es-8 were made from backcross progeny of the mating (LEJ/Hkm x T/Hok)F1 x LEJ/Hkm. One recombinant in 51 progeny tested was observed between Es-2 and Es-7; however, recombination between Es-2 and Es-8 was not observed in the same progeny. In addition, we show that the esterase polymorphisms of Es-5 in liver homogenate and Es-3 in small intestine homogenate are identical.