Question: how does the kidney function in the presence of a high concentration of the hormone oxytocin?
First of all, oxytocin is one of two hormones formed by the neuronal cells of the hypothalamic nuclei and stored in the posterior lobe of the hypophysis (posterior pituitary), the other being vasopressin. Both hormones stimulate contraction of muscular tissue, and vasopressin is an antidiuretic hormone (stimulating water reabsorption) that plays an important role in urine formation. Oxytocin is important in partuition and is used to induce active labor. Hence, the interest on the role of oxytocin as an antidiuretic hormone.
We have used a pde model [Am. J. Physiol. (Renal Fluid Electrolyte Physiol. 38), 269 (1995), F70-F77] to study the concentration dependence of hormone action. The model uses in vitro measurements of water permeability of a segment of the rat nephron (inner medullary collecting duct) in the presence of varying concentrations of oxytocin to predict urine concentration. The result is that it is shown that circulating (picomolar) concentrations of oxytocin can play a role in regulation of water balance, with the conclusion that oxytocin can function physiologically as an antidiuretic hormone.
Neural nets have been used for many learned tasks, including perceptrons, parallel processing, prediction of protein secondary structure, and prediction of membrane-spanning protein topology. Using a class of models ["Neural Net Models to Characterize Integral Membrane Proteins - Preliminary Report", ICIAM 95 Proceedings, Akademie-Verlag, IV (1996), 39-42] (file "Mejia_ICIAM95.tar.Z" at ftp://ftp.ncifcrf.gov/smb/pubs/), we describe an approach to determine extracellular, cytosolic and membrane spanning domains from the amino acid sequence of integral membrane proteins.