Evidence for a predominant form of Mr = 15,000 prosomatostatin in the mouse hypothalamus. Relationship with somatostatin-14 and -28.

This paper demonstrates the presence of a single predominant form of high molecular weight somatostatin (Mr congruent to 15,000) in mouse hypothalamus as judged by a combination of purification procedures including molecular sieve filtration, reverse phase high pressure liquid chromatography, isoelectric focusing, and gel electrophoresis under denaturing conditions. Furthermore, the conversion of the Mr = 15,000 somatostatin species by hypothalamic enzyme activities led to the formation of both somatostatin-14 and -28 which were identified by high pressure liquid chromatography. No evidence was found for the presence of molecular species containing the sequence of the (Tyr-7, Gly-10) derivative of somatostatin. These observations suggest that, in contrast to the situation encountered in the pancreas, a predominant form of prosomatostatin is synthesized in hypothalamic neurones. They indicate that, in the hypothalamus, both the tetradecapeptide and somatostatin-28 derive from a single prohormone.