Myelin basic protein present in the acid extracts of rat hypothalami releases insulin and glucagon from isolated rat pancreatic islets.
The insulinotropic and glucagon-releasing activity of acid extracts of rat hypothalami were tested in two bioassay systems using short-time incubation of isolated rat pancreatic islets and a rat insulinoma (RIN) cell line. Release of insulin and glucagon into the incubation medium was measured by radioimmunoassay. The major insulin-releasing and glucagon-releasing activity eluted in a broad zone in Sephacryl S-200 gel filtration in 30% acetic acid corresponding to the molecular weights between approximately 10 and 40 kD. The highest activity was eluted in a zone corresponding to 14 kD and was purified to homogeneity by means of two steps of reversed-phase HPLC. Amino acid analysis and SDS polyacrylamide gel electrophoresis indicated that the biologically active material was the rat small (myelin) basic protein characterized previously by Dunkley & Carnegie (1974). The purified rat hypothalamic material showed insulinotropic and glucagon-releasing activity indistinguishable from that of purified porcine myelin basic protein, and lost its insulinotropic activity when incubated with anti-myelin basic protein immunosorbent. We conclude that the major insulin-releasing and glucagon-releasing activity in acid extracts of the high-molecular-weight fractions of rat hypothalami is myelin basic protein.
Leppäluoto
J
J
Department of Physiology, University of Oulu, Finland.
Zeytin
F
F
Ueno
N
N
Ying
S Y
SY
Ling
N
N
Guillemin
R
R
D000596:Amino Acids / Q000032:analysis; D000818:Animals; D001681:Biological Assay; D002461:Cell Line, Transformed; D005934:Glucagon / Q000378:metabolism*; D007031:Hypothalamus / Q000032:analysis*; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007340:Insulinoma / Q000378:metabolism; D007515:Islets of Langerhans / Q000378:metabolism*; D008970:Molecular Weight; D004676:Myelin Basic Protein / Q000008:administration & dosage* / Q000302:isolation & purification; D009500:Neutralization Tests; D010190:Pancreatic Neoplasms / Q000378:metabolism; D011863:Radioimmunoassay; D051381:Rats; D014020:Tissue Extracts / Q000008:administration & dosage* / Q000032:analysis
D000596:Amino Acids; D007328:Insulin; D004676:Myelin Basic Protein; D014020:Tissue Extracts; D005934:Glucagon