Glucose transport in chronically altered rat nephrons.

Microinjection experiments were performed in anesthetized rats to study the tubular absorptive capacity for glucose (TG) in normal and chronically altered tubules, i.e., tubules that sustained anatomical repair and compensatory changes of their previously normal configuration after acute damage. TG was complete when the glucose load injected in normal or altered early or late proximal convolutions was less than or equal to 1.5 or less than or equal to 10 pmol . s-1, respectively. In normal tubules, TmG was 10 and 5 pmol . s-1 after early and late proximal microinjections, respectively. After early proximal microinjections in altered tubules, different levels of TmG were found. They related to the degree of compensatory growth. TmG was approximately 12, 24, or 35 pmol . s-1, respectively, in altered tubules with minor, moderate, or major compensatory growth. After late proximal microinjections, TmG was 15 pmol . s-1. TG variability was greater in altered than in normal tubules. Correlation between structural and functional compensatory changes was thus demonstrated. Furthermore, an important, albeit latent, absorptive capacity for glucose of the proximal straight tubule was found.