Immunoreactive and biologically active somatostatin in human and sheep milk

Abstract

The presence of immunoreactive and biologically active somatostatin in sheep and human milk has been demonstrated. Milk somatostatin exhibits similar chromatographic behavior to that of synthetic somatostatin-14 on both reversed-phase C1 8 and cation-exchange high-performance liquid chromatography columns. Milk, in contrast to plasma, contains only somatostatin-14-like material. Milk somatostatin was capable of inhibiting the basal and the prostaglandin-induced release of growth hormone from anterior pituitary cell cultures in a pattern similar to synthetic somatostatin-14. The concentrations of the peptide, as determined by radioimmunoassay, were found to be 11 3 pg/ml in human milk and 150 4.8 pg/ml (mean f range) in sheep milk. These values are severalfold higher than the corresponding concentration of the peptide in the plasma of these species. These findings are analogous to our previous observations concerning two other hypothalamic hormones, luliberin and thyroliberin [Baram, T., Koch, Y., Hazum, E. and Fridkin, M. (1977) Science (Wash. D C ) 198, 300-3021. The high concentration of somatostatin and other neuropeptides in milk implies either an active concentrating mechanism in the mammary gland or an additional extrahypothalamic source for the synthesis and release of these peptides.The extrahypothalamic distribution of somatostatin (SS), the growth-hormone-release-inhibiting factor, has been extensively reported [l -51. The finding that, in addition to the hypothalamus, a number of organs or tissues are involved in the synthesis of somatostatin, has been well established. The broad spectrum of biological effects exerted by this peptide [6] aroused much interest in the evaluation of its location and concentration in body tissues and fluids.Hormones are natural constituents of milk of various mammals [7]. Recently the presence of epidermal growth factor in human milk [8] and of opiate-like compounds in bovine milk [9] were reported. We and others have reported on immunoreactive and bioactive materials resembling luteinizing-hormone-releasing hormone (luliberin) and thyrotropin-releasing hormone (thyroliberin) in the milk of man, cow and rat [lo-131. It was found that the concentrations of these peptides in milk are significantly higher than the corresponding hormone levels in plasma [lo].We now report the presence of somatostatin in the milk of man and sheep. Comparative characterization of this peptide, along with synthetic, hypothalamic-like, somatostatin-14, has been carried out by chromatographic, radioimmunological and biological studies.Correspondence to Y . Koch MATERIALS AND METHODS Preparation of milk extractSheep milk was obtained from the Veterinary Institute, Beit Dagan, Israel, and human colostrum was obtained from the Department of Obstetrics and Gynecology, Wolfson Hospital, Bat-Yam, Israel. Human and sheep milk were defatted by centrifugation at 15000 rpm for 30 min at 4°C. Casein and other proteins were coagulated by acidification to pH 4 and removed by centrifugation. Defatted/de-casein...

Digested formula but not digested fresh human milk causes death of intestinal cells in vitro: implications for necrotizing enterocolitis

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Somatostatin Levels in Plasma in Nonsmoking and Smoking Breast‐Feeding Women

“…It has been shown to inhibit the release of prolactin, which stimulates milk production, from the pituitary (5) and it inhibits gastrointestinal functions including the release of gastrointestinal hormones (6). Somatostatin is present in milk, indicating that it may be produced in the mammary glands (7).…”

Thyrotropin‐Releasing Hormone Mediates Growth Hormone Release Induced by Milk and Nursing in Neonatal Rats

“…This finding is consistent with the TRH as a GRF in neonatal rats 667 species difference in the concentration of milk-borne TRH. Rat milk appears to be particularly rich in certain peptidc hormones since day 2 rat milk contains about 20-fold higher concentrations of immunoreactive SRIF than human or ovine milk (4,12). While G H R H and SRIF in vivo regulate basal G H secretion in neonatal rats as carly as day 2 postpartum (8,(13)(14)(15), these neurohormones are not modulated by maternal Factors (8).…”