Subcellular distribution of somatostatin-14, somatostatin-28 and somatostatin-28 (1-12) in rat brain cortex and comparisons of their respective binding sites in brain and pituitary.
Subcellular distribution and binding characteristics of the three endogenous peptides somatostatin-14 (SRIF-14), somatostatin-28 (SRIF-28) and somatostatin-28(1-12) (SRIF-28(1-12] derived from preprosomatostatin were investigated in the rat brain cortex. The three peptides are predominantly recovered from a crude mitochondrial pellet (P2), containing the pinched off nerve endings. Specific high affinity binding sites for 125I-N-Tyr-SRIF-14 and 125I-N-Tyr-SRIF-28 are present on pituitary and brain membranes. Under the same conditions, 125I-N-Tyr-SRIF-28(1-12) binding is undetectable. Moreover, SRIF-28(1-12) does not displace 125I-N-Tyr-SRIF-14 or 125I-N-Tyr-SRIF-28 binding. SRIF-28 is more potent than SRIF-14 to displace 125I-N-Tyr-SRIF-28 binding to brain and pituitary membranes, while both peptides are equipotent to displace 125I-N-Tyr-SRIF-14 binding. Finally, the regional distribution of 125I-N-Tyr-SRIF-14 and 125I-N-Tyr-SRIF-28 binding sites in the brain is identical. In conclusion, the present results are consistent with a neurotransmitter and neurohormonal role for SRIF-14 and SRIF-28. The function of SRIF-28(1-12) in brain remains to be elucidated. Additionally, a differential role for SRIF-14 and SRIF-28 both in adenohypophysis and brain cannot be ascertained at the present time.
D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D002540:Cerebral Cortex / Q000378:metabolism*; D008297:Male; D010446:Peptide Fragments / Q000378:metabolism; D010902:Pituitary Gland / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013004:Somatostatin / Q000378:metabolism*; D053561:Somatostatin-28; D013347:Subcellular Fractions / Q000378:metabolism; D014018:Tissue Distribution
D010446:Peptide Fragments; D013004:Somatostatin; D053561:Somatostatin-28; C037197:somatostatin 28-(1-12)