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Phylogenetic aspects of somatostatin in the gastroenteropancreatic (GEP) endocrine system
Phylogenetic Aspects of Somatostatin in the Gastroenteropancreatic (GEP) Endocrine System Sture
Falkmer.
Robert
P. Elde,
Claes
Hellerstrijm,
and
Birger
Petersson
T
HE EVOLUTION of the somatostatin (SRIF)-producing cells in the gastroenteropancreatic (GEP) endocrine system is incompletely unknown. To determine whether SRIF is a phylogenetically young or old hormone, radioimmunologic assays of acid-ethanol extracts of the GEP endocrine system of some invertebrates and lower vertebrates were made, and the results were correlated with observations made in a concomitant light microscopic investigation, mainly focused on the reliability of the Hellerstriim-Hellman modification of the Davenport procedure for visualizing the D cells.’ The present report summarizes these observations and supplements them by a more comprehensive immunocytochemical investigation using the peroxidase-antiperoxidase (PAP) procedure. MATERIALS
AND
METHODS
Most of the details about the animals used, the organs and tissues investigated, and nomenclature investigation
employed have been previously described.’
can be obtained. The present supplementary
and the techniques
From Table 1 an ideaof the extent of the
study mainly concerns the possibility of de-
tract and in the parenchyma of some associated glands in a few protostomian and deuterostomian invertebrates, as well as in cartilaginous and bony fish, by means of the PAP procedure using previously described techniques2.” For comparison, insulin- and glucagon-producing cells were demonstrated in adjacent sections from the same tissues, again using previously described techniques.’ The results were correlated with those obtained previously by conventional light microscopy staining procedures and by radioimmunoassays of acid-ethanol extracts of the same tissue specimens.’ tecting SRIF-producing
D cells in the mucosa of the alimentary
RESULTS
AND
DISCUSSION
As seen in Table 1, SRIF in the GEP endocrine system appears to be a hormone that occurs in all vertebrates and is limited to some of those invertebrates that belong to the same evolutionary line as the vertebrates, i.e., the deuterostomian. Neither by radioimmunoassays and immunocytochemical procedures, nor by the nonimmunologic histologic staining procedures was it possible to detect any SRIF-storing D cells in the mucosa of the alimentary tract and the parenchyma of associated glands of any of the animals belonging to the protostomian evolution line. However, insulin-producing cells have previously been found in several tissues of protostomian species, as well as in deuterostomian invertebrates.s This finding could (to some extent) be confirmed by the PAP procedure in the present study. When compared with insulin, therefore, SRIF is a phylogenetically more recent hormone.‘.” In previous studies on the evolution of insulin- and glucagon-producing cells,” From the Department of Pathology, University of Umed, Urned. Sweden; the Department of Anatomy, University of Minnesota School of Medicine, Minneapolis. Minn., and the Department of Histology. University of Uppsala. Uppsala. Sweden. Supported by grams from theswedish Medical Research Council (Projects 12X-718 and 12X-109). Address reprint requests to Prof Siure Falkmer, Institute ofPathology, S-901 87 Ume86, Sweden. o 1978 by Grune & Stratton. Inc. 0026 -0495/78/27/3~0010%01.00/0 Metabolism. Vol. 27. No. 9. Suppl. 1 (September). 1978
1193
1194
FALKMER
ET AL
PHYLOGENETIC
ASPECTS
1195
IN GEP SYSTEM
Table 1. Summarizing
Review of Some Observations
Made in Present Study
and Preceding Investigation.
0
0
0
0
0
0
0
0
0
0
>
0
0
0
0
0
7
0
0
0
0
0
>
0
132t.
i+1
ItI
0
(+I
I+)
5
0
0
7.800
+
0
1.108t
+
+
103
I+1
3.800
+ 0
212.000 3.500* 17.000 1.246 302t 21.850$
(+I +
+
0
+
+
+
0
+
+
+
+
+
I+1
+
(+I
the most original B and A cells occur as endocrine cells of the open type in the mucosa of the alimentary tract. It is not until the evolutionary stage of the cyclostomes that a separate islet organ (without exocrine acinar pancreatic parenchyma) is formed, originating from the bile-duct mucosa (in the hagfish) or the gut mucosa (in the lamprey).” In this original islet parenchyma and in the bile-duct mucosa no glucagon-producing A cells have been found. In the cyclostomes these cells still occur as endocrine cells of the open type, restricted to the gastrointestinal mucosa, and the predominant cell type in islet tissue is the insulin-producing B ce11.5 Some of the B cells still occur as endocrine cells of the closed type in the bile-duct mucusa, but at that evolutionary stage none are left in the gastroin-
Fig. 1. Medium-power photomicrographs of the pancreas (A, B, C) and the mucosa of the corpus region of the stomach (D) in a cartilaginous fish, the spiny dogfish, Squalus acanthies. All the sections have been immunocytochemically processed by the PAP procedure to visualize SRIF-storing D cells (A. D), insulin-producing B cells (6). and glucagon-containing A cells (C). From panels A, B. and C it is clear that no marked differences exist batween the topographic distributions of the A, B, and D cells. They all occur both in the duct-associated islet parenchyma and in the epithelium of the pancreatic ducts. essentially as endocrine cells of the closed type. In the stomach mucosa, however, most of the D cells are of the open type, mainly localized to the surface epithelium (top). To some extent, however, they also occur in the epithelium of the glands (bottom) x 380.
1196
FALKMER
ET AL.
testinal mucosa.” The A cells do not spread into the islet parenchyma until a pancreatic gland is formed at the evolutionary stage of the cartilaginous fish. Still, some A cells persist in the gastrointestinal mucosa in mammals.’ The present results confirm these observations with regard to the B and A cells and show, in addition, that the SRIF-storing D cells seem to undergo a similar development. Thus, in the gastrointestinal mucosa they occur as endocrine cells of the open type.” At the evolutionary stage of the cyclostomes they have already invaded the bile-duct mucosa to a great extent” as endocrine cells of the closed type and have started to spread into the islet parenchyma.‘,“.” There, in the hagfish, they still constitute only about 1% of the total ceil mass ~-~a morphologic approximation that is confirmed by comparison between the amounts of insulin and SRIF produced by excised hagfish islet organs.’ Consequently, it seems that the D cells occupy an intermediate position between the B and A cells in the evolution of the GEP endocrine system. ‘L” When the results of the PAP procedure are compared with those of the nonimmunologic Hellerstrom-Hellman method, the previously made preliminary observations” are confirmed. From Table 1 it is obvious that when the GEP endocrine system in lower vertebrates and in invertebrates is analyzed for the presence of D cells, the Hellerstrom-Hellman method is inferior to the PAP procedure. When it works adequately, as in the cartilaginous fish, it gives results similar to those with the PAP technique and correlates well with radioimmunologic observations of SRIF in the tissues.’ However, even the PAP procedure did not give satisfactorily pictures of the D cells in the gastrointestinal mucosa of the invertebrates, e.g., that of the tunicate Cionu intrstinalis. The discrepancy between the results of the PAP procedure and those of the radioimmunoassays observed in the gastrointestinal mucosa of the bony fish Cottus scorpius and, to some extent, in the amphioxus, are difficult to explain. Considering the fact that SRIF-storing cells occur in the gastrointestinal mucosa of all the other lower vertebrates, it seems rather exceptional that D cells would be absent from that part of the GEP endocrine system in Cott~s .scorpius. This finding could indicate that in the highly developed Euteleost fish, to which C’ottus belongs, evolution has proceeded further, so that almost all the D cells have left the gastrointestinal mucosa. REFERENCES I.
Falkmer
S, Elde R, Hellerstriim
Some phylogenetical of somatostatin endocrine
in the gastro-entero-pancreatic
system.
munocytochemical tative
C, et al:
aspects on the occurrence A
histological
and
im-
assays of tissue ex-
tracts. Arch Histol Jpn 40:99
calization of somatostatin hypothalamus. 3. Parsons
J, Erlandsen
Central
and peripheral
statin.
Immunoenzyme
studies. J Histochem
lo-
in cell bodies of the rat
Am J Anat 144541
548, 1975
S, Hegre
localization
0.
et al:
of somato-
immunocytochemical
Cytochem
somatostatin
0,
Parsons
J. et al: of cell
and gastrin within the D cell. J His-
tochem Cytochem 24:883 5. Falkmer S, &tberg phology of pancreatic
117, 1977 (Suppl)
2. Elde R, Parsons J: lmmunocytochemical
S. Hegre
islet cell hormones distribution
types in the islet and evidence for the presence of
study, combined with quanti-
radioimmunological
4. Erlandsen Pancreatic
24:872~ 882. 1976
Wellman York,
897, 1976 Y: Comparative
mor-
islets in animals, in Volk B.
KF (eds): The Diabetic
Pancreas.
New
Plenum. 1977, pp 15 60
6. Falkmer Entero-insular
S, &tberg
A clue to hormone Gut Hormones. Symposium,
Y,
Van
Noorden
S:
endocrine systems of cyclostomes: evolution? in Bloom SR (ed):
Proceedings of the International Lausanne,
Edinburgh. Churchill
June
Livingstone,
18 -19,
1977.
1977. pp 57 63
Falkmer.
Robert
P. Elde,
Claes
Hellerstrijm,
and
Birger
Petersson
T
HE EVOLUTION of the somatostatin (SRIF)-producing cells in the gastroenteropancreatic (GEP) endocrine system is incompletely unknown. To determine whether SRIF is a phylogenetically young or old hormone, radioimmunologic assays of acid-ethanol extracts of the GEP endocrine system of some invertebrates and lower vertebrates were made, and the results were correlated with observations made in a concomitant light microscopic investigation, mainly focused on the reliability of the Hellerstriim-Hellman modification of the Davenport procedure for visualizing the D cells.’ The present report summarizes these observations and supplements them by a more comprehensive immunocytochemical investigation using the peroxidase-antiperoxidase (PAP) procedure. MATERIALS
AND
METHODS
Most of the details about the animals used, the organs and tissues investigated, and nomenclature investigation
employed have been previously described.’
can be obtained. The present supplementary
and the techniques
From Table 1 an ideaof the extent of the
study mainly concerns the possibility of de-
tract and in the parenchyma of some associated glands in a few protostomian and deuterostomian invertebrates, as well as in cartilaginous and bony fish, by means of the PAP procedure using previously described techniques2.” For comparison, insulin- and glucagon-producing cells were demonstrated in adjacent sections from the same tissues, again using previously described techniques.’ The results were correlated with those obtained previously by conventional light microscopy staining procedures and by radioimmunoassays of acid-ethanol extracts of the same tissue specimens.’ tecting SRIF-producing
D cells in the mucosa of the alimentary
RESULTS
AND
DISCUSSION
As seen in Table 1, SRIF in the GEP endocrine system appears to be a hormone that occurs in all vertebrates and is limited to some of those invertebrates that belong to the same evolutionary line as the vertebrates, i.e., the deuterostomian. Neither by radioimmunoassays and immunocytochemical procedures, nor by the nonimmunologic histologic staining procedures was it possible to detect any SRIF-storing D cells in the mucosa of the alimentary tract and the parenchyma of associated glands of any of the animals belonging to the protostomian evolution line. However, insulin-producing cells have previously been found in several tissues of protostomian species, as well as in deuterostomian invertebrates.s This finding could (to some extent) be confirmed by the PAP procedure in the present study. When compared with insulin, therefore, SRIF is a phylogenetically more recent hormone.‘.” In previous studies on the evolution of insulin- and glucagon-producing cells,” From the Department of Pathology, University of Umed, Urned. Sweden; the Department of Anatomy, University of Minnesota School of Medicine, Minneapolis. Minn., and the Department of Histology. University of Uppsala. Uppsala. Sweden. Supported by grams from theswedish Medical Research Council (Projects 12X-718 and 12X-109). Address reprint requests to Prof Siure Falkmer, Institute ofPathology, S-901 87 Ume86, Sweden. o 1978 by Grune & Stratton. Inc. 0026 -0495/78/27/3~0010%01.00/0 Metabolism. Vol. 27. No. 9. Suppl. 1 (September). 1978
1193
1194
FALKMER
ET AL
PHYLOGENETIC
ASPECTS
1195
IN GEP SYSTEM
Table 1. Summarizing
Review of Some Observations
Made in Present Study
and Preceding Investigation.
0
0
0
0
0
0
0
0
0
0
>
0
0
0
0
0
7
0
0
0
0
0
>
0
132t.
i+1
ItI
0
(+I
I+)
5
0
0
7.800
+
0
1.108t
+
+
103
I+1
3.800
+ 0
212.000 3.500* 17.000 1.246 302t 21.850$
(+I +
+
0
+
+
+
0
+
+
+
+
+
I+1
+
(+I
the most original B and A cells occur as endocrine cells of the open type in the mucosa of the alimentary tract. It is not until the evolutionary stage of the cyclostomes that a separate islet organ (without exocrine acinar pancreatic parenchyma) is formed, originating from the bile-duct mucosa (in the hagfish) or the gut mucosa (in the lamprey).” In this original islet parenchyma and in the bile-duct mucosa no glucagon-producing A cells have been found. In the cyclostomes these cells still occur as endocrine cells of the open type, restricted to the gastrointestinal mucosa, and the predominant cell type in islet tissue is the insulin-producing B ce11.5 Some of the B cells still occur as endocrine cells of the closed type in the bile-duct mucusa, but at that evolutionary stage none are left in the gastroin-
Fig. 1. Medium-power photomicrographs of the pancreas (A, B, C) and the mucosa of the corpus region of the stomach (D) in a cartilaginous fish, the spiny dogfish, Squalus acanthies. All the sections have been immunocytochemically processed by the PAP procedure to visualize SRIF-storing D cells (A. D), insulin-producing B cells (6). and glucagon-containing A cells (C). From panels A, B. and C it is clear that no marked differences exist batween the topographic distributions of the A, B, and D cells. They all occur both in the duct-associated islet parenchyma and in the epithelium of the pancreatic ducts. essentially as endocrine cells of the closed type. In the stomach mucosa, however, most of the D cells are of the open type, mainly localized to the surface epithelium (top). To some extent, however, they also occur in the epithelium of the glands (bottom) x 380.
1196
FALKMER
ET AL.
testinal mucosa.” The A cells do not spread into the islet parenchyma until a pancreatic gland is formed at the evolutionary stage of the cartilaginous fish. Still, some A cells persist in the gastrointestinal mucosa in mammals.’ The present results confirm these observations with regard to the B and A cells and show, in addition, that the SRIF-storing D cells seem to undergo a similar development. Thus, in the gastrointestinal mucosa they occur as endocrine cells of the open type.” At the evolutionary stage of the cyclostomes they have already invaded the bile-duct mucosa to a great extent” as endocrine cells of the closed type and have started to spread into the islet parenchyma.‘,“.” There, in the hagfish, they still constitute only about 1% of the total ceil mass ~-~a morphologic approximation that is confirmed by comparison between the amounts of insulin and SRIF produced by excised hagfish islet organs.’ Consequently, it seems that the D cells occupy an intermediate position between the B and A cells in the evolution of the GEP endocrine system. ‘L” When the results of the PAP procedure are compared with those of the nonimmunologic Hellerstrom-Hellman method, the previously made preliminary observations” are confirmed. From Table 1 it is obvious that when the GEP endocrine system in lower vertebrates and in invertebrates is analyzed for the presence of D cells, the Hellerstrom-Hellman method is inferior to the PAP procedure. When it works adequately, as in the cartilaginous fish, it gives results similar to those with the PAP technique and correlates well with radioimmunologic observations of SRIF in the tissues.’ However, even the PAP procedure did not give satisfactorily pictures of the D cells in the gastrointestinal mucosa of the invertebrates, e.g., that of the tunicate Cionu intrstinalis. The discrepancy between the results of the PAP procedure and those of the radioimmunoassays observed in the gastrointestinal mucosa of the bony fish Cottus scorpius and, to some extent, in the amphioxus, are difficult to explain. Considering the fact that SRIF-storing cells occur in the gastrointestinal mucosa of all the other lower vertebrates, it seems rather exceptional that D cells would be absent from that part of the GEP endocrine system in Cott~s .scorpius. This finding could indicate that in the highly developed Euteleost fish, to which C’ottus belongs, evolution has proceeded further, so that almost all the D cells have left the gastrointestinal mucosa. REFERENCES I.
Falkmer
S, Elde R, Hellerstriim
Some phylogenetical of somatostatin endocrine
in the gastro-entero-pancreatic
system.
munocytochemical tative
C, et al:
aspects on the occurrence A
histological
and
im-
assays of tissue ex-
tracts. Arch Histol Jpn 40:99
calization of somatostatin hypothalamus. 3. Parsons
J, Erlandsen
Central
and peripheral
statin.
Immunoenzyme
studies. J Histochem
lo-
in cell bodies of the rat
Am J Anat 144541
548, 1975
S, Hegre
localization
0.
et al:
of somato-
immunocytochemical
Cytochem
somatostatin
0,
Parsons
J. et al: of cell
and gastrin within the D cell. J His-
tochem Cytochem 24:883 5. Falkmer S, &tberg phology of pancreatic
117, 1977 (Suppl)
2. Elde R, Parsons J: lmmunocytochemical
S. Hegre
islet cell hormones distribution
types in the islet and evidence for the presence of
study, combined with quanti-
radioimmunological
4. Erlandsen Pancreatic
24:872~ 882. 1976
Wellman York,
897, 1976 Y: Comparative
mor-
islets in animals, in Volk B.
KF (eds): The Diabetic
Pancreas.
New
Plenum. 1977, pp 15 60
6. Falkmer Entero-insular
S, &tberg
A clue to hormone Gut Hormones. Symposium,
Y,
Van
Noorden
S:
endocrine systems of cyclostomes: evolution? in Bloom SR (ed):
Proceedings of the International Lausanne,
Edinburgh. Churchill
June
Livingstone,
18 -19,
1977.
1977. pp 57 63