Islet p-cells

Metyrapone is useful in testing the endocrine functioning of the a cells of pancreatic islets P cells of pancreatic islets Neurohypophysis Pituitary-adrenal axis Leydig s cells of the testes... 

The CGRP family of peptides includes the 37-amino acid neurotransmitter CGRP, the 52-amino acid adreno-medullin, found predominantly in vascular cells and adrenal tissue and the 37-amino acid amylin found in pancreatic islet p-cells. These peptides share a 6-amino acid ring structure, formed by an intramolecular disulfide bridge. 

The absorption of sulfonylureas from the upper gastrointestinal tract is fairly rapid and complete. The agents are transported in the blood as protein-bound complexes. As they are released from protein-binding sites, the free (unbound) form becomes available for diffusion into tissues and to sites of action. Specific receptors are present on pancreatic islet p-cell surfaces which bind sulfonylureas with high affinity. Binding of sulfonylureas to these receptors appears to be coupled to an ATP-sensitive K+ channel to stimulate insulin secretion. These agents may also potentiate insulin-stimulated glucose transport in adipose tissue and skeletal muscle. 

The current concept of autoimmune diabetes is that pancreas islet P cells are destroyed by an autoimmune response mediated by T lymphocytes that react specifically to one or more P cell proteins (Bach, 1994). Figure 25.1 shows the pathogenesis of type 1 diabetes. This concept gave rise to the idea that auto-immune diabetes can be prevented by the manipulation of autoreactive T cells or... 

Silva AM, Liu-Gentry J, Dickey AS et al (2005) a-Latrotoxin increases spontaneous and depolarization-evoked exocytosis from pancreatic islet P-cells. J Physiol 565 783-99 Siu R, Fladd C, Rotin D (2006) N-cadherin is an in vivo substrate for PTPo and partidpates in PTPo-mediated inhibition of axon growth. Mol Cell Biol 27 208-19 Smith DS, Russell FE (1966) Structure of the venom gland of the black widow spider Latrodectus mactans. A preliminary light and electron microscopic study. In Russell FE, Saunders PR (eds) Animal Toxins, Oxford, Pergamon, pp 1-15... 

Figure 5.12. Regulation of insulin secretion by glucose in the pancreatic islet p-cell. An increase in glucose will yield increased ATP levels, which in turn will close the Kj. channels and partially depolarize the membrane. Opening of voltage-gated Ca channels will trigger exocytosis of insulin.

Hybridization on sections of human pancreas with oligonucleotide probes designed to hybridize with the P2-AR mRNA showed expression in islet P-cells but not in the exocrine tissue of the pancreas (51). In situ hybridization with digoxygenin-labeled oligonucleotide probes revealed the presence of the mRNA of the p3-AR subtype in the smooth muscle of the urinary bladder (77,78). There was a predominant expression of P3-AR mRNA in human bladder tissue, with... 

The rate of transport of metabolites into the cell has profound effects on the net metabolic rate of many cells. Insulin, a polypeptide hormone synthesized by the islet p-cells of the pancreas, increases the maximum rate of glucose transport by a factor of three to four. The result is that the metabolic activity of the cell is greatly increased. 

A role for this iPLA2 in the control of insulin secretion from pancreatic islet P-cells... 

It is mostly beneficial in the treatment of selected cases of non-insulin-dependent diabetes melitus (NIDDM). Interestingly, only such patients having some residual functional islet P-cells which may be stimulated by this drug shall afibrd a positive response. Therefore, it is quite obvious that such subjects who essentially need more than 40 Units of insulin per day normally will not respond to this drug. 

Both GLP-1 and GIP are able to regulate glucose homeostasis by interacting with G-protein-coupled receptors (GPCR) [56, 57], The GIP receptor is mainly expressed on islet p cells, but it also occurs in adipose tissue and in the central nervous system. Conversely, the GLP-1 receptor is localized on islet a and p cells and in... 

Gross RW, Ramanadham S, Kruska KK, Han X, Turk J. Rat and human pancreatic islet cells contain a calcium ion independent phospholipase A2 activity selective for hydrolysis of arachidonate which is stimulated by adenosine trisphosphate and is specifically localized to islet p-cells. Biochemistry 1993 32 327-336. 

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