The Effect of Cell Volume on Mammary Gland Metabolism

Grant, Alastair C. G (2001) The Effect of Cell Volume on Mammary Gland Metabolism. PhD thesis, University of Glasgow.

Abstract

1. It is becoming increasingly apparent that cell volume, otherwise termed the cellular hydration state, regulates processes such as protein synthesis, lipogenesis and membrane transport. In this study, the effect of cell volume perturbations on mammary cell metabolism has been investigated. Thus, the effect of cell swelling and shrinking on protein synthesis and lipogenesis in rat mammary tissue has been examined. In addition, the effect of cell volume changes on the free cytosolic calcium concentration ([Ca2+]i) in rat mammary acinar cells has been studied. 2. Mammary tissue (explants and acini) isolated from lactating rats during peak lactation was used in this study. Protein synthesis was studied by measuring the incorporation of radiolabelled amino acids into trichloroacetic acid precipitable material. Cell swelling, induced by a hyposmotic shock markedly increased protein synthesis in mammary tissue explants and acini. Conversely, cell shrinking, induced by a hyperosmotic shock markedly inhibited protein synthesis in mammary explants and acini. The effect of cell swelling and shrinking on protein synthesis was a) dependent upon the extent of the osmotic challenge and b) reversible. Swelling- induced mammary protein synthesis was dependent upon the presence of extracellular calcium. In this connection, thapsigargin and tBHQ markedly inhibited volume- sensitive protein synthesis suggesting that protein synthesis is dependent upon luminal calcium stores. Isosmotic cell swelling, induced by using buffers containing urea significantly increased mammary protein synthesis. 3. The effect of cell volume perturbations on the [Ca2+]i in mammary acinar cells isolated from rats during peak lactation was examined. The [Ca2+]i was measured using the fura-2 dye technique. Cell swelling, induced by a hyposmotic challenge, increased the [Ca2+]i in a fashion that was transient. The effect of a hyposmotic shock on the [Ca2+]i was dependent upon the extent of the osmotic perturbation. The hyposmotically-induced increase in the [Ca2+]i could not be attributed to a) a change in the trans-membrane sodium gradient or b) a change in the ionic strength of the incubation buffer. Removing extracellular Ca2+ (using EGTA) inhibited the effect of a hyposmotic shock on the [Ca2+]i in rat mammary acinar cells, suggesting that a hyposmotic challenge increases the influx of Ca2+ rather than a release of Ca2+ from intracellular stores Thapsigargin increased the size of the volume-sensitive increase m the [C

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Additional Information: Adviser: D B Shennan
• Keywords: Biochemistry, Physiology
• Date of Award: 2001
• Depositing User: Enlighten Team
• Unique ID: glathesis:2001-76090
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 19 Nov 2019 16:50
• Last Modified: 19 Nov 2019 16:50
• URI: https://theses.gla.ac.uk/id/eprint/76090