Role for the beta-adrenoceptor-coupled adenylate cyclase in the ontogenetic subsensitivity to isoproterenol in the embryonic chick ventricle
Isoproterenol (ISO) increases contractility and cyclic AMP content in ventricles of embryonic and hatched chicks. A transient decrease in beta-agonist sensitivity for both effects is seen in 18 day embryos (10E). Beta-adrenoceptor-coupled adenylate cylase (AC) and receptor binding were characterized in 14,000xg particulates and purified membranes from the ventricles of 10-11E, 17-19E and week-old chicks (5-6H). In crude particulates, the K/sub act/ for ISO (+100 ..mu..M Gpp(NH)p)-stimulated AC is greatest in the 17-19E. Maximal (ISO + Gpp(NH)p)-AC of the 11E is two-fold greater and NaF-AC is 30% greater than those of the 17-19E and 5-6 H. All age groups have comparable catalytic AC. All age groups have comparable K/sub d/'s for /sup 3/H-dihydroalprenolol (5-11 nM), while the 18E has 40% fewer receptors than the 11E and 5-6H. In particulates or membranes, K/sub act/ values for Gpp(NH)p, NaF, MnCl> and forskolin are unchanged with age. In membranes, K/sub act/ values for ISO plus guanine nucleotide (G) and maximal (ISO + G)-AC are similar in all ages. The net effect of ISO ((ISO + G) minus G) is least while that of G (G minus basal) is greatest in the 18E. Whereas /sup 32/P-labeling of a 42 kd protein by cholera toxin is lowest (25% decrease) in particulates of the 18E, labeling of a 39-41 kd doublet by pertussis toxin decreases continuously (by 50%) with age. All age groups have comparable K/sub d/'s (10-13 pM) for (/sup 125/I)-cyanopindolol (CYP). These data indicate that a transient decrease in receptor number and receptor-N/sub s/ (guanine nucleotide-sensitive) coupling in the 18E contribute to the subsensitivity to beta-agonist.
- Research Organization:
- Connecticut Univ., Storrs (USA)
- OSTI ID:
- 6936169
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CYCLASES
BIOCHEMISTRY
HEART
BIOCHEMICAL REACTION KINETICS
PHYSIOLOGY
AMP
CELL MEMBRANES
CHICKENS
EMBRYOS
ENZYME ACTIVITY
IODINE 125
ONTOGENESIS
PHOSPHORUS 32
RECEPTORS
TRACER TECHNIQUES
TRITIUM COMPOUNDS
ANIMALS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIRDS
BODY
CARDIOVASCULAR SYSTEM
CELL CONSTITUENTS
CHEMISTRY
DAYS LIVING RADIOISOTOPES
ELECTRON CAPTURE RADIOISOTOPES
ENZYMES
FOWL
INTERMEDIATE MASS NUCLEI
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
LABELLED COMPOUNDS
LIGHT NUCLEI
LYASES
MEMBRANE PROTEINS
MEMBRANES
NUCLEI
NUCLEOTIDES
ODD-EVEN NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ORGANS
PHOSPHORUS ISOTOPES
PROTEINS
RADIOISOTOPES
REACTION KINETICS
VERTEBRATES
550201* - Biochemistry- Tracer Techniques