Inositol lipid turnover and compartmentation in canine trachealis smooth muscle
We established conditions for the study of metabolism and compartmentation of inositol phospholipids in canine trachealis muscle. Unstimulated muscle was incubated with myo-(3H)inositol for 30 min at 37 degrees C which resulted in labeling of the tissue free myo-inositol pool, whereas only a small amount of radioactivity was incorporated into inositol phospholipids or inositol phosphates. After addition of 5.5 microM carbachol, phosphatidylinositol (PI), phosphatidylinositol-4-phosphate (PIP), and phosphatidylinositol-4,5-bisphosphate (PIP2), specific radioactivities increased exponentially, reaching apparent constant values in 180-240 min. Initial rates of increases in PI, PIP, and PIP2 specific radioactivities were 39, 32, and 66 times that measured in unstimulated muscle. Metabolic flux rates (nmol.100 nmol total lipid Pi-1.min-1) during development of force averaged 0.42 +/- 0.09 and during force maintenance averaged 0.14 +/- 0.01. Fractions of total PI, PIP, and PIP2 pools that were linked to muscarinic cholinergic activation were estimated to be 0.97, 0.85, and 0.65, respectively. Initial rates of increase in specific radioactivities and specific radioactivities during carbachol activation were similar in PI, PIP, and PIP2 fast active compartments, suggesting metabolic flux from PI to PIP to PIP2 was in near chemical equilibrium. Turnover times for PI, PIP, and PIP2 fast active compartments were estimated to be 21, 1.6, and 4.0 min, respectively.
- Research Organization:
- Univ. of Pennsylvania School of Medicine, Philadelphia (USA)
- OSTI ID:
- 6326726
- Journal Information:
- Am. J. Physiol.; (United States), Journal Name: Am. J. Physiol.; (United States) Vol. 256; ISSN AJPHA
- Country of Publication:
- United States
- Language:
- English
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59 BASIC BIOLOGICAL SCIENCES
ANIMALS
CARBOHYDRATES
DOGS
ESTERS
IN VITRO
INOSITOL
INOSITOLS
ISOTOPE APPLICATIONS
LABELLED COMPOUNDS
LIPIDS
MAMMALS
METABOLISM
MONOSACCHARIDES
MUSCLES
ORGANIC COMPOUNDS
ORGANIC PHOSPHORUS COMPOUNDS
PHOSPHOLIPIDS
RESPIRATORY SYSTEM
SACCHARIDES
TRACER TECHNIQUES
TRACHEA
TRITIUM COMPOUNDS
VERTEBRATES