Role of kidney and liver in the renotropic activity generated in rats after uninephrectomy

Abstract

Following uninephrectomy the remnant kidney undergoes a compensatory growth apparently regulated by a humoral renotropic factor(s). Our studies were carried out to assess the role of renal and hepatic tissue in the generation of such a renotropic factor(s). The renotropic activity in extracts of rat kidney and liver obtained at different times after uninephrectomy was assayed in cortical tubules from rat kidney removed 24 h after uninephrectomy. We found that kidney extracts from 6 h and 24 h uninephrectomized rats increased [3H]thymidine incorporation into tubular cell DNA, dose-dependently, compared to those from sham-operated rats. Maximal stimulation was observed at 10(4)-fold (6 h) or 10(2)-fold (24 h) extract dilution. This activity was undetected in perfused kidney extracts, or in extracts of kidneys from simultaneously uninephrectomized and partially hepatectomized rats. However, only 10-fold dilution of unperfused liver extract from 6 h or 24 h uninephrectomized rats showed significant activity. Kidney or liver extracts from 30 min uninephrectomized animals failed to display activity. Our results point to an extrarenal origin for the humoral renotropic activity generated after uninephrectomy, although the kidney seems to modulate this activity.