1. Cysteamine induces a loss of tissue somatostatin-28 when measured as somatostatin-28(15-28)-like immunoreactivity but not when assessed as somatostatin-28(1-14)-like immunoreactivity: evidence for the importance of the disulfide bond for cysteamine action
Y C Patel, I Pierzchala Endocrinology. 1985 May;116(5):1699-702. doi: 10.1210/endo-116-5-1699.
The reported loss of somatostatin-14 (S-14)-like immunoreactivity (LI) by cysteamine (CSH) could be mediated through an action on the S-14 disulfide bond. If so, then in the case of somatostatin-28 (S-28) (a linear 14 amino acid N-terminally extended form of S-14), it should be possible to demonstrate with region-specific antisera, a selective effect of CSH on the disulfide bond containing C-terminal half of the molecule. To obtain evidence for this, we have determined by RIAs, the effect of CSH on S-28 concentration measured separately as S-28(15-28) LI and S-28(1-14) LI in the jejunal mucosa, a tissue rich in S-28. Four hours after a single sc injection of CSH to rats, mucosal S-28(15-28) LI was reduced from 16.4 +/- 0.6 to 4.6 +/- 0.51 pmol/mg protein (P less than 0.01). By contrast, S-28(1-14) LI sustained no loss and in fact increased from 27.6 +/- 1.9 to 41.6 +/- 2.2 pmol/mg protein (P less than 0.01). On Sephadex G-50 columns (in 6 M urea) approximately 70% of S-28(15-28) LI and S-28(1-14) LI coeluted with synthetic S-28 marker. These data suggest that CSH acts on the 15-28 segment of the S-28 molecule and renders it nonimmunoreactive probably through interaction with the disulfide bond. This mechanism probably also accounts for CSH-induced S-14 loss.
2. Cytochemical demonstration of somatostatin 28-(1-14)-like immunoreactivity in the rat hypothalamus and gastro-entero-pancreatic endocrine system
T Iwanaga, S Ito, Y Yamada, T Fujita Endocrinology. 1983 Nov;113(5):1839-44. doi: 10.1210/endo-113-5-1839.
Somatostatin-28 (SS 28) is a NH2-terminally extended form of somatostatin-14 (SS 14). Using an antiserum whose antigenic determinant is contained in segment 1-14 of SS 28, the cellular localization of a SS 28-(1-14)-like immunoreactivity was examined in the hypothalamus and gastro-enteropancreatic endocrine system of the rat. Immunoreactivity for SS 28-(1-14) was recognized in the SS 14-immunoreactive nerve cells of the hypothalamus and their axons terminating in the median eminence. Electron microscopic immunocytochemistry revealed that SS 28-(1-14)-like immunoreactivity in the median eminence was localized in the secretory granules of a type of nerve terminal. The immunoreactive cells in the gastro-enteropancreatic endocrine system also corresponded to the SS 14-immunoreactive D cells. Only in the pyloric antrum, however, did SS 14-immunoreactive D cells show no or very weak reactivity to the anti-SS 28-(1-14) serum. The wide distribution of SS 28-(1-14)-like immunoreactivity in the same cellular elements as those containing SS 14 supports the view that SS 28 is a precursor of SS 14.
3. Somatostatin 28(1-14) immunoreactivity in primary afferent neurons of the rat spinal cord
R H Ho, M Berelowitz Neurosci Lett. 1984 May 4;46(2):161-6. doi: 10.1016/0304-3940(84)90435-x.
Somatostatin 28(1-14) immunoreactivity is present in dorsal root ganglion cells and in the superficial laminae of the spinal cord in the rat. The distribution of somatostatin 28(1-14) immunoreactive varicosities in the dorsal horn corresponds well to the distribution of somatostatin 14 immunoreactive elements. Some dorsal root ganglion cells exhibit both somatostatin 14 and somatostatin 28(1-14) immunoreactivities.
