Somatomedin C in the pancreas of young and adult, normal and obese, hyperinsulinemic mice.
Immunocytochemical, immunochemical and RNA-hybridization techniques were used to map the distribution of somatomedin C (Sm-C; insulin-like growth factor I; IGF-I) in the pancreas of young and adult lean and obese mice. The D cells in the islets of Langerhans showed intense cytoplasmic Sm-C immunoreactivity, extending into their processes. Only slight Sm-C immunoreactivity was seen in A and B cells, apparently confined to the plasma membranes. In the exocrine pancreas scattered duct cells were immunopositive. Starvation increased, while feeding decreased the Sm-C immunoreactivity in B cells. RNA-hybridization analyses revealed that roughly the same number of Sm-C mRNA molecules, as calculated per DNA amount in the pancreas, could be demonstrated in young and adult, lean and obese mice. Radioimmunoassay (RIA) determinations of total Sm-C showed that there were about equal concentrations in the pancreas of lean and obese mice. There were marked differences between the liver and the pancreas, in that the RIA Sm-C values for the former were twice those in the latter while, in contrast, the corresponding values for the Sm-C mRNA, i.e. the agent determining the synthesis of Sm-C, were about 100 times higher in the liver as compared to that in the pancreas. We interpret our results as follows: The D cells in the islets form and secrete Sm-C in both young and adult, lean and obese mice, while A and B cells bind, but do not necessarily synthesize this peptide.(ABSTRACT TRUNCATED AT 250 WORDS)
Hansson
H A
HA
Department of Histology, University of Göteborg, Sweden.
Edwall
D
D
Löwenadler
B
B
Norstedt
G
G
Paleus
S
S
Skottner
A
A
D000818:Animals; D005260:Female; D006946:Hyperinsulinism / Q000378:metabolism*; D007150:Immunohistochemistry; D007334:Insulin-Like Growth Factor I / Q000276:immunology / Q000378:metabolism*; D051379:Mice; D008815:Mice, Inbred Strains / Q000378:metabolism*; D008820:Mice, Obese / Q000378:metabolism*; D009693:Nucleic Acid Hybridization; D010179:Pancreas / Q000032:analysis / Q000276:immunology / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D011863:Radioimmunoassay; D013002:Somatomedins / Q000378:metabolism*; D013045:Species Specificity
D012333:RNA, Messenger; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I