The biological activity of catfish pancreatic somatostatin.
Catfish pancreatic somatostatin, which contains eight additional amino acids on the amino terminus of a tetradecapeptide with considerable homology to tetradecapeptide somatostatin (SRIF), is a naturally occurring homolog of the hypothalamic peptide. The purpose of these studies was to determine the biological activity of this somatostatin homolog. Inhibition of 125I-labelled tyr1-SRIF binding to bovine pituitary plasma membranes by catfish pancreatic somatostatin was approximately 33% that of SRIF. Pancreatic somatostatin had full biological activity measured by inhibition of growth hormone release from isolated rat pituitary cells, but 0.01-0.1% the potency of SRIF. Pancreatic somatostatin at 100 ng/ml produced a 50-60% inhibition of insulin and glucagon secretion from perfused rat pancreas, while SRIF produced comparable inhibition at 10 ng/ml. This report demonstrates that a larger molecular form and natural homolog of SRIF, isolated from fish pancreas, has the same (but reduced) biological activities in rat assay systems as somatostatin originally isolated from sheep hypothalamus.
D000595:Amino Acid Sequence; D000818:Animals; D001681:Biological Assay; D002417:Cattle; D002462:Cell Membrane / Q000378:metabolism; D005399:Fishes; D005934:Glucagon / Q000378:metabolism; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D010179:Pancreas / Q000032:analysis* / Q000378:metabolism; D010902:Pituitary Gland / Q000378:metabolism; D051381:Rats; D011956:Receptors, Cell Surface / Q000378:metabolism; D017481:Receptors, Somatostatin; D013004:Somatostatin / Q000494:pharmacology*
D007328:Insulin; D011956:Receptors, Cell Surface; D017481:Receptors, Somatostatin; D013004:Somatostatin; D005934:Glucagon