| Mechanisms of fluid and ion secretion by the parotid gland of the kangaroo, Macropus rufus, assessed by administration of transport-inhibiting drugs. | |
| | |
MedLine Citation:
|
PMID: 8576452 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
|
Possible mechanisms of primary fluid formation by macropodine parotid glands were investigated in anaesthetized red kangaroos using ion transport inhibitors. Carotid plasma amiloride concentrations of 0.05-0.5 mmol.l-1 progressively reduced a stable acetylcholine-evoked half-maximal flow rate of 2.0 +/- 0.04 to 0.22 +/- 0.024 ml.min-1 (mean +/- SEM). Concurrently, saliva bicarbonate concentration and secretion fell (135 +/- 1.6 to 67 +/- 1.7 mmol.l-1 and 272 +/- 7.6 to 15 +/- 2.6 mumol.min-1, respectively); [phosphate], [chloride] and [sodium] rose and [potassium] and osmolality were unaltered. High-rate cholinergic stimulation did not increase saliva flow beyond 11 +/- 1.0% of that for equivalent pre-amiloride stimulation. Equipotent levels of amiloride and methazolamide given concurrently were no more effective at blocking flow and bicarbonate secretion than when given separately. Furosemide (up to 2 mmol.l-1), bumetanide (up to 0.2 mmol.l-1) and ethacrynate (1 mmol.l-1) in carotid plasma had no effect on salivary flow or ion concentrations. During methazolamide blockade, furosemide did not curtail the concurrent increase in salivary [chloride]. Chlorothiazide at 0.25-1.0 mmol.l-1 caused progressive depression of saliva flow and [bicarbonate], and elevation of [chloride]. 4-acetamido-4'-isothiocyanatostilbene-2,2'disulphonic acid at 0.1 mmol.l-1 was without effect, whereas at 0.5 mmol.l-1 it stimulated fluid secretion and increased saliva [protein], [sodium], [potassium], [bicarbonate] and osmolality. Concurrently, mean arterial blood pressure and pulse pressure fell and heart rate, haematocrit and carotid artery plasma flow rose. These responses were absent if saliva flow was kept constant by reduction in cholinergic stimulation during 4-acetamido-4-isothiocyanatostilbene-2,2'disulphonic acid administration. It is concluded that secretion of primary fluid by the kangaroo parotid is initiated mainly (> 90%) by secretion of bicarbonate which is formed in the endpiece cells from CO2 delivered by the circulation. No evidence was found for initiation of fluid secretion by chloride transport involving basolateral Na(+)-K(+)-2Cl- symports, Na(+)-Cl- symports or Cl-/HCO3- antiports. |
| | |
Authors:
|
A M Beal |
Publication Detail:
|
Type: Journal Article; Research Support, Non-U.S. Gov't |
Journal Detail:
|
Title: Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology Volume: 165 ISSN: 0174-1578 ISO Abbreviation: J. Comp. Physiol. B, Biochem. Syst. Environ. Physiol. Publication Date: 1995 |
Date Detail:
|
Created Date: 1996-03-11 Completed Date: 1996-03-11 Revised Date: 2009-06-08 |
Medline Journal Info:
|
Nlm Unique ID: 8413200 Medline TA: J Comp Physiol B Country: GERMANY |
Other Details:
|
Languages: eng Pagination: 396-405 Citation Subset: IM |
Affiliation:
|
School of Biological Science, University of New South Wales, Sydney, Australia. |
Export Citation:
|
APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
|
Amiloride
/
metabolism,
pharmacology Animals Bicarbonates / metabolism Blood Pressure / physiology Bumetanide / metabolism, pharmacology Carotid Arteries / physiology Chlorothiazide / metabolism, pharmacology Diuretics / metabolism, pharmacology* Electrolytes / blood, metabolism Ethacrynic Acid / metabolism, pharmacology Female Furosemide / metabolism, pharmacology Heart Rate / physiology Ion Transport / drug effects* Macropodidae / physiology Male Methazolamide / metabolism, pharmacology Osmolar Concentration Parotid Gland / drug effects, secretion* Regional Blood Flow / physiology Saliva / drug effects, metabolism |
| Chemical | |
Reg. No./Substance:
|
0/Bicarbonates; 0/Diuretics; 0/Electrolytes; 2609-46-3/Amiloride; 28395-03-1/Bumetanide; 54-31-9/Furosemide; 554-57-4/Methazolamide; 58-54-8/Ethacrynic Acid; 58-94-6/Chlorothiazide |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
Previous Document: Lipoprotein lipase activity and its relationship to high milk fat transfer during lactation in grey ...
Next Document: The impact of dietary fats, photoperiod, temperature and season on morphological variables, torpor p...