α2U-Globulin: Measurement in rat kidney following administration of 2,2,4-trimethylpentane

Abstract

Hyaline droplet formation was stimulated markedly in the kidneys of post-puberty male rats 24–48 h after a single oral dose of 12/24 mmol/kg 2,2,4-trimethylpentane [TMP]. Renal hyaline droplet formation could not be detected in female rats or in pre-puberty male rats following similar doses of TMP. A dose-dependent increase in the renal concentration of the androgen-dependent low molecular weight protein, α 2U-globulin was observed in post-puberty male rats 24 h after a single oral dose of TMP, over the range 0.3–12.0 mmol/kg. After administration of a single dose of 12 mmol/kg TMP to male rats, the renal concentration of α 2U-globulin rose steadily up to a peak after 48 h and then returned slowly to near normal after 7 days. Renal α 2U-globulin could not be detected in female rats and in pre-puberty male rats. An immunocytochemical assay was developed to examine the distribution of α 2U-globulin within the kidney. α 2U-Globulin was localised primarily in the S2 segment of renal proximal tubules in untreated male rats. Rats which received a single dose of 12 mmol TMP/kg showed not only a greater staining intensity, due to the presence of a higher concentration of α 2U-globulin, but also staining in adjacent segments of the renal cortex. Several urinary biochemical indicators of nephrotoxicity were measured daily in male rats for up to 72 h following a single dose of 12 mmol TMP/kg. Renal proximal tubular function was unimpaired by TMP treatment. On the basis of studies in untreated and TMP-treated rats, a strong association has been found between the presence of renal hyaline droplets and the occurrence of renal α 2U-globulin. The findings in the present study provide an explanation for the occurrence of renal hyaline droplets only in adult male rats, but do not, as yet, establish the toxicological significance of increases in renal hyaline droplet formation.