Abstract
This chapter examines the phenotypic expression and natriuretic peptide-activated chloride secretion in cultured shark rectal gland (SRG) epithelial cells. Elasmobranchs living in seawater have plasma solute concentrations that are isoosmotic or somewhat hyperosmotic to their marine environment. The SRG consists largely of simple and branched, blind-ended secretory tubules that radiate from a central duct. The central duct presumably serves as a simple excretory conduit and is lined by a stratified epithelium, which is 4–6 cells thick. The simple columnar cells of the secretory tubules exhibit extensive basolateral plasma membrane interdigitations and a rich population of mitochondria. The Cl − secretory properties of cultured SRG cells maintained on permeable supports have been investigated in detail using electrophysiologic methods. Cl − secretion is determined by calculating the equivalent short-circuit current after measuring transepithelial voltage and resistance. It has been found that in the perfused SRG, somatostatin and neuropeptide Y nearly completely inhibit forskolin-stimulated Cl − secretion.
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