Active urea transport by the skin of Bufo viridis: Amiloride- and phloretin-sensitive transport sites

Journal Article · Thu Sep 01 00:00:00 EDT 1988 · American Journal of Physiology; (USA)

OSTI ID:6974838

Rapoport, J; Abuful, A; Chaimovitz, C; Noeh, Z; Hays, R M ^[1]

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1. Soroka Medical Center, Beersheva (Israel) Albert Einstein College of Medicine, New York, NY (USA)

Urea is actively transported inwardly (J{sub i}) across the skin of the green toad Bufo viridis. J{sub i} is markedly enhanced in toads adapted to hypertonic saline. The authors studied urea transport across the skin of Bufo viridis under a variety of experimental conditions, including treatment with amiloride and phloretin, agents that inhibit urea permeability in the bladder of Bufo marinus. Amiloride (10{sup {minus}4} M) significantly inhibited J{sub i} in both adapted and unadapted animals and was unaffected by removal of sodium from the external medium. Phloretin (10{sup {minus}4} M) significantly inhibited J{sub i} in adapted animals by 23-46%; there was also a reduction in J{sub i} in unadapted toads at 10{sup {minus}4} and 5 {times} 10{sup {minus}4} M phloretin. A dose-response study revealed that the concentration of phloretin causing half-maximal inhibition (K{sub {1/2}}) was 5 {times} 10{sup {minus}4} M for adapted animals. J{sub i} was unaffected by the substitution of sucrose for Ringer solution or by ouabain. They conclude (1) the process of adaptation appears to involve an increase in the number of amiloride- and phloretin-inhibitable urea transport sites in the skin, with a possible increase in the affinity of the sites for phloretin; (2) the adapted skin resembles the Bufo marinus urinary bladder with respect to amiloride and phloretin-inhibitable sites; (3) they confirm earlier observations that J{sub i} is independent of sodium transport.

• OSTI ID: 6974838
• Journal Information: American Journal of Physiology; (USA), Vol. 255:3; ISSN 0002-9513
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
CARBON 14 COMPOUNDS
MEMBRANE TRANSPORT
DIURETICS
BIOLOGICAL EFFECTS
SKIN
PERMEABILITY
UREA
BIOCHEMICAL REACTION KINETICS
BLADDER
DOSE-RESPONSE RELATIONSHIPS
OUABAIN
TOADS
AMIDES
AMPHIBIANS
ANIMALS
AQUATIC ORGANISMS
BODY
CARBOHYDRATES
CARBONIC ACID DERIVATIVES
CARDIAC GLYCOSIDES
CARDIOTONICS
CARDIOVASCULAR AGENTS
DRUGS
GLYCOSIDES
KINETICS
LABELLED COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANS
REACTION KINETICS
STROPHANTHINS
URINARY TRACT
VERTEBRATES
551001* - Physiological Systems- Tracer Techniques