Fig. 4. Expression of the PP hormone in somatostatin-producing cells in Arx^-/Pax4^-/- animals after the onset of feeding. Pancreas was isolated 12 hours after birth either from normally fed pups (P12h-fed; A-F) or from starved animal separated from their mother after delivery (P12h-not fed; G-L). Every tenth section of wild-type and Arx/Pax4 double mutant pancreas (indicated on the left side) was labelled with anti-somatostatin (A,B,G,H) and anti-PP (C,D,I,J) antibodies, and the number of marked cells was quantified; merged pictures of the different staining are presented in E,F and K,L. A quantification of the endocrine modifications between the two genotypes, estimated using Student's t-test, is provided in percent under each set of pictures (n3, P<0.05; U, unchanged). In normally fed P12h Arx/Pax4 double mutants, note the more than fivefold increase in PP production by the excess somatostatin-producing cells, when compared with wild type (E,F). Importantly, in starved animals, the content in PP-marked cells was found to be normal when compared with controls (K,L).