Regional Distribution of Immunoreactive Somatostatin in the Bovine Pineal Gland

Abstract

Regional distribution of immunoreactive somatostatin (IRS) and melatonin were investigated in the bovine pineal gland. The total IRS and melatonin content ranged from 0.26 to 2.28 pmol, and from 19.4 to 42.7 pmol, respectively, per bovine pineal. Reverse phase liquid chromatography of pineal extracts demonstrated that more than 90% of IRS coeluted with synthetic somatostatin-14 and somatostatin-28. While the IRS content was shown to vary considerably throughout the gland, with a constant and marked maximal concentration at the proximal end of the pineal, the maximal melatonin concentration appeared in the central part of the gland, coinciding with the total protein distribution. The existence of the highest levels of pineal IRS near the habenular commissure, where the afferent fibers of the central pinealopetal innervation enter the gland, suggests that pineal somatostatin may be, at least in part, of neural origin.

Somatostatinand Prosomatostatin Immunoreactive Nerve Fibers in the Bovine Pineal Gland

“…9). The presence of both somatostatin-14 and somatostatin-28 is in accord with previous HPLC analysis of bo vine extract [9] in which analysis it was shown that 90% of the somatostatin immunoreactive extract coeluted with these two somatostatin molecules. The positive staining with antiserum No.…”

“…This finding is also in accord with an analysis of bovine somatostatin immunoreactive material from the same re gions [9] in which study the rostral part of the gland was shown to contain a higher concentration of somatostatinimmunoreactive material than the distal part of the gland. These findings, together with the observation that fibers from the pineal stalk are connected with intrapineal nerve fibers, strongly indicate a somatostatinergic central in nervation of the pineal in the bovine.…”

“…Thus, after tissue extractions followed by radioimmuno assay, somatostatin immunoreactivity has been demon strated in the pineal gland of the rat [3][4][5][6][7], hamster, gerbil, mouse [7,8], cow [9], and man [10]. However, the immunohistochemical localization of pineal somato statin has given equivocal results.…”

Generation of the Melatonin Endocrine Message in Mammals: A Review of the Complex Regulation of Melatonin Synthesis by Norepinephrine, Peptides, and Other Pineal Transmitters

“…The presence of SOM in the pineal gland was shown for the first time by Pelletier et al (1975) in the rat (and later on by Pévet et al, 1980b;Finley et al, 1981;Webb et al, 1984;Møller et al, 1995) then in the hamster, gerbil, mouse (Webb et al, 1984), sheep, pig (Lew and Lawson-Willey, 1987), cow (Peinado et al, 1989;Møller et al, 1992), and human (Bouras et al, 1987). The rat pineal gland contains approximately 0.3 to 3 ng SOM/mg protein (Webb et al, 1985).…”

“…The SOMergic fibers are not of sympathetic origin since the pineal content of SOM is not modified after SCGx (Webb et al, 1984(Webb et al, , 1985. It is proposed that these fibers could be of central origin because the number of SOMergic fibers and the peptide concentration are 4 times higher in the MULTIPLE REGULATION OF PINEAL MELATONIN SYNTHESIS IN MAMMALS proximal than in the distal area of the gland (Peinado et al, 1989;Møller et al, 1992).…”