Maake C et al. (1998), An immunohistochemical and morphometric analysi...

XB-ART-15091

Gen Comp Endocrinol 1998 May 01;1102:182-95. doi: 10.1006/gcen.1998.7064.

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An immunohistochemical and morphometric analysis of insulin, insulin-like growth factor I, glucagon, somatostatin, and PP in the development of the gastro-entero-pancreatic system of Xenopus laevis.

Maake C , Hanke W , Reinecke M .

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The ontogeny of the classical islet hormones insulin (INS), glucagon (GLUC), somatostatin (SOM), and pancreatic polypeptide (PP) as well as insulin-like growth factor I (IGF-I) in the gastro-entero-pancreatic (GEP) system of Xenopus laevis (stages 41-66) was studied using double immunofluorescence and morphometric analysis. As early as stage 41, clustered INS-immunoreactive (-IR) and isolated GLUC-IR cells occurred in the pancreas. The first SOM-IR cells appeared at stage 43, followed by PP-IR cells at stage 46. About 79% of the PP immunoreactivity was confined to a subpopulation of the GLUC-IR cells. Both the GLUC/PP-IR cells and the PP-IR cells were located in a distinct area of the pancreas. The first islets occurred in premetamorphosis (around stage 50) and comprised mainly INS-IR and GLUC-IR cells. The majority of SOM-IR, PP-IR, and GLUC/PP-IR cells was dispersed. The numbers of hormone cells remained quite constant until the end of prometamorphosis (stage 58). Around stages 60-62, the islets were partly disintegrated and the numbers of islet cells slightly decreased. At stage 63, the cell number began to increase and reached the levels typical for the adult around stage 66. After metamorphic climax, the islets were reformed. In the gastrointestinal tract, transient INS-IR cells occurred prior to the adaptation of the gastrointestinal tract to feeding (stages 41-44) and during metamorphosis when there is remodeling of the gastrointestinal tract (stages 60-63). Therefore, INS released from the transient mucosal INS-IR cells may be involved in the temporary proliferation of mucosal epithelial cells. The first GLUC-IR and SOM-IR cells were seen at stage 41. PP-IR cells followed at stage 46. In contrast to the islets, GLUC-IR and PP-IR cells constituted different cell populations. Around stage 46, the first IGF-I immunoreactions appeared in the GEP-system. In pancreas, IGF-I immunoreactivity was found in the GLUC/PP-IR, cells (85-99%) but was absent from INS-IR, GLUC-IR, and SOM-IR cells. The IGF-I-IR gastro-entero-endocrine cells, however, seemed to contain none of the classical islet hormones.

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Species referenced: Xenopus laevis
Genes referenced: gcg grhl3 grn igf1 ins pnma2 ppy sst.1

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	FIG. 1. Number of all subpopulations of classical islet hormone containing cells per 0.1 mm2 pancreatic tissue in Xenopus during development.
	FIG. 2. Number of the different subtypes of GLUC-IR cells per 0.1 mm2 pancreatic tissue in Xenopus during development.
	FIG. 3. Endocrine cells in the GEP-system of X. laevis during early development (stages 41–43). (a) Some INS immunoreactive cells form a small islet in the exocrine pancreas (P); gut (G). 3300. (b) Transient INS immunoreactive cells occur in the stomach (S) mucosal epithelium. 3480. (c) GLUC immunoreactive cells are present dispersed throughout the exocrine pancreas (P) and in the stomach (S) mucosal epithelium (arrow).3280. (d) Several SOM immunoreactive cells are found in the stomach (S) mucosal epithelium. 3240.
	FIG. 4. Occurrence of the classical islet hormones in X. laevis GEP system at stage 50 (premetamorphosis) as revealed by double immunofluorescence on consecutive sections. The first section is incubated with antisera against INS (a) and GLUC (b) and the second against SOM (c) and PP (d). (a) INS-IR cells occur in a small islet and singularly. (b) GLUC-IR cells are found distributed throughout the exocrine pancreas and in the stomach (S) mucosal epithelium (arrowhead). (c) SOM immunoreactivity is present in a cell of the pancreas (arrowhead) and in endocrine cells of the stomach (S) and the gut (G). (d) Some PP cells occur in the right part of the pancreas. Some of these show coexistence with GLUC immunoreactivity (arrows). 3120.
	FIG. 5. Occurrence of the classical islet hormones in X. laevis pancreas at stage 60 (metamorphic climax) as revealed by double immunofluorescence on consecutive sections. The first section is incubated with antisera against INS (a) and GLUC (b) and the second against SOM (c) and PP (d). (a) Most INS-IR cells are accumulated in small islets. (b, c) GLUC-IR and SOM-IR cells are distributed throughout the pancreas. Some GLUC-IR cells (arrows) exhibit PP immunoreactivity in coexistence (d). 3200.
	FIG. 6. Occurrence of the classical islet hormones in X. laevis pancreas at stage 66 (end of metamorphic climax) as revealed by double immunofluorescence on consecutive sections. The first section is incubated with antisera against INS (a) and GLUC (b) and the second against SOM (c) and PP (d). (a) The vast majority of INS-IR cells form bigger islets. (b) Numerous GLUC-IR cells are found in all areas of the pancreas. GLUC-IR cells in the left portion contain PP immunoreactivity (d) (arrows) while the other GLUC-IR cells (arrowheads) do not. (c) Few dispersed SOM-IR cells are present. 380.
	FIG. 7. Immunohistochemical localisation of GLUC, PP, and IGF-I (stage 65) on consecutive sections by double immunofluorescence. The first section is incubated with antisera against GLUC (a) and PP (b) and the second against GLUC (c) and IGF-I (d). The GLUC immunoreactive cells contain PP and IGF-I immunoreactivity. 3380.
	FIG. 8. Partial coexistence of GLUC (a) and IGF-I (b) immunoreactivities in the GEP system at stage 66 as revealed by double immunofluorescence. Part of the pancreatic glugagon-immunoreactive cells also contain IGF-I immunoreactivity (arrows) but others (arrowheads) and the stomach GLUC immunoreactive cells (S) do not. 3440.