Rats Homozygous for the grc Complex Have Defective Transport of Androgen-binding Protein to the Epididymis, but Normal Secretion into the Blood’

Male rats homozygous for the growth and reproduction complex (grc), which is closely linked to the major histocompatibility complex, are sterile due to a uniform arrest of spermatogenesis after formation of primary spermatocytes. The present study was conducted to determine whether grc influenced the secretion of the Sertoli cell product androgen-binding protein (rABP) in two F, hybrid crosses. One was an F, hybrid of the RiO and ACP strains and the other was an F, hybrid population derived from the R16 and BI strains. These crosses were chosen because they allowed examination of the effects of grc on rABP secretion when this gene complex was associated with two different major histocompatibiity complex backgrounds. In both crosses the rABP content of testes and epididymides from rats homozygous for grc were markedly reduced whereas heterozy-gotes were normal. By contrast, the concentration of rABP in plasma was normal or near normal at all ages. These observations are compatible with the hypothesis that grc influences the secretion of rABP from the apical portion of Sertoli cells into the tubular lumen and its subsequent transport to the epididymis, but has little or no effect on rABP secretion from the base of Sertoli cells into the blood. In other studies we have shown that infertile animals that have received prenatal x-ray or that are heterozygous for the H1’ gene have patterns of rABP secretion similar to that of gre/gre homozygotes. It is therefore possible that the abnormal rABP secretion into tubular lumen in these animals is secondary to germ cell depletion, which is a factor common to grc/grc, Hre/+, and x-ray-treated rats