We examined endothelin-1 (ET-1) regulation of the xenobiotic efflux pump, multidrug resistance-associated protein isoform 2 (MRP2), in intact dogfish shark rectal salt gland tubules using a fluorescent substrate sulforhodamine 101 and confocal microscopy. Subnanomolar to nanomolar concentrations of ET-1 rapidly reduced the cell-to-lumen transport of sulforhodamine 101. These effects were prevented by an ET(B) receptor antagonist but not by an ET(A) receptor antagonist. Immunostaining with an antibody to mammalian ET(B) receptors showed specific localization to the basolateral membrane of the shark rectal gland epithelial cells. ET-1 effects on transport were blocked by a protein kinase C (PKC)-selective inhibitor, implicating PKC in ET-1 signaling. A protein kinase A (PKA)-selective inhibitor had no effect. Forskolin reduced luminal accumulation of sulforhodamine 101, but inhibition of PKA did not block the forskolin effect. Consistent with this observation, a cAMP analog that does not activate PKA reduced luminal accumulation of sulforhodamine 101. These results indicate that shark rectal gland transport on MRP2 is regulated by ET acting through an ET(B) receptor and PKC. In addition, cAMP affects transporter function through a PKA-independent mechanism, possibly by competition for transport.
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http://dx.doi.org/10.1152/ajpregu.00333.2001 | DOI Listing |
Braz J Biol
November 2024
Instituto Federal de Educação, Ciência e Tecnologia do Espírito Santo - IFES-Piúma, Piúma, ES, Brasil.
Kidney360
March 2024
Mount Desert Island Biological Laboratory, Bar Harbor, Maine.
Pictured, described, and speculated on, for close to 400 years, the function of the rectal gland of elasmobranchs remained unknown. In the late 1950s, Burger discovered that the rectal gland of Squalus acanthias secreted an almost pure solution of sodium chloride, isosmotic with blood, which could be stimulated by volume expansion of the fish. Twenty five years later, Stoff discovered that the secretion of the gland was mediated by adenyl cyclase.
View Article and Find Full Text PDFMar Pollut Bull
July 2021
Laboratório de Organismos Aquáticos, Universidade Federal do Maranhão (UFMA), Brazil.
Contamination by metals is among the most pervasive anthropogenic threats to the environment. Despite the ecological importance of marine apex predators, the potential negative impacts of metal bioaccumulation and biomagnification on the health of higher trophic level species remains unclear. To date, most toxicology studies in sharks have focused on measuring metal concentrations in muscle tissues associating human consumption and food safety, without further investigating potential impacts on shark health.
View Article and Find Full Text PDFAm J Physiol Cell Physiol
May 2021
Renal Section, Department of Medicine, Yale University School of Medicine, New Haven, Connecticut.
Adenosine receptors (ADORs) are G protein-coupled purinoceptors that have several functions including regulation of chloride secretion via cystic fibrosis transmembrane conductance regulator (CFTR) in human airway and kidney. We cloned an ADOR from (shark) that likely regulates CFTR in the rectal gland. Phylogenic and expression analyses indicate that elasmobranch ADORs are nonolfactory and appear to represent extant predecessors of mammalian ADORs.
View Article and Find Full Text PDFEvid Based Complement Alternat Med
October 2020
Noncommunicable Diseases Research Center, Fasa University of Medical Sciences, Fasa, Iran.
Ulcerative colitis (UC) is one of the most well-known types of inflammatory bowel disease that manifests as recurrent inflammation of rectum and colon. The goal of this study is to evaluate the protective effects of shark liver oil (SLO) on acetic acid-induced ulcerative colitis in rats. Eighty induced UC rats were randomly divided into ten equal groups and received the following treatments for seven days: 1 ml of normal saline rectally, 1 ml of gel base (carboxymethyl cellulose) rectally, 10 mg/kg of Asacol rectally, 10 mg/kg of mesalazine orally, 5% gel form of SLO rectally, 10% gel form of SLO rectally, 200 mg of SLO orally, and 400 mg of SLO orally.
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