Fig. 6. The activation of Erk MAP kinases in the ureteric bud is reduced markedly when kidneys are incubated in the presence of function-blocking antibodies to GDNF. (A) The top panel shows a western blot of ureteric buds, isolated after a 7 hour incubation of complete kidneys with and without anti-GDNF, probed with an antibody specific for phosphorylated Erk1/2 (Erk-P). Much less phosphorylation is seen in ureteric buds of kidneys treated with anti-GDNF. The bottom panel shows the same samples probed with an antibody that recognises both phosphorylated and non-phosphorylated Erk, and shows that anti-GDNF treatment does not alter the amounts of Erk protein present in the cells. The blot was prepared after just 7 hours so that net ureteric bud volume would not have changed significantly. (B,C) Micrographs of kidneys cultured in normal medium (B) and anti-GDNF (C) for 48 hours confirm that the anti-GDNF antibody blocks ureteric bud morphogenesis.
