when glomerular filtration was markedly reduced or stopped by ureteral obstruction , the renal extraction of proinsulin , insulin , and c-peptide was invariably greater than the simultaneously measured extraction of inulin , indicating that these polypeptides are removed from the renal circulation by both glomerular filtration and direct uptake from peritubular capillary blood .
C0033362
proinsulin
C0006558
c-peptide