In vivo effect of 3,5,3 prime -triiodothyronine on calcium uptake in several tissues in the rat: Evidence for a physiological role for calcium as the first messenger for the prompt action of thyroid hormone at the level of the plasma membrane
- Hebrew Univ. Hadassah Medical School, Jerusalem (Israel)
Calcium has been shown in vitro to serve as the first messenger for the rapid effect of thyroid hormone at the level of the plasma membrane. In the present study the physiological relevance of this mechanism is examined in the whole animal. To this end, the effect of T3 on 45calcium uptake and sugar 2-deoxyglucose (2-DG) uptake, an effect that requires extracellular calcium, and the influence of calcium blockers thereon were measured in ventricles, atria, diaphragm, fat, and liver in the rat. In the first three tissues, T3 produced comparable changes in 45Ca uptake and 2-DG uptake (T3 increased 2-DG uptake in fat, where 45Ca uptake was undetected, and had no effect in liver); this activity was blocked by the calcium channel blocker cadmium. The effect of T3 on 45Ca uptake, like its effect on the in vivo uptake of 2-DG described previously, was biphasic and time related; at physiological doses of 0.01 and 0.1 micrograms/100 g BW, T3 increased 45Ca uptake, whereas at greater (pharmacological) doses of 1 and 100 micrograms/100 g BW, T3 was without effect or inhibited 45Ca uptake. In ventricles and atria, the stimulatory effect of T3 on 45Ca uptake was very rapid within 2 min, at which time it was at or near maximum (50-90% above control) and then declined gradually and was not seen after 10-20 min. Of the several calcium blockers employed, verapamil (organic) and cadmium (inorganic) were found to be the most effective. Verapamil and cadmium produced a rapid, transient, and dose-related inhibition of 45Ca uptake in the tissues examined (except fat tissue where, under the experimental conditions employed, 45Ca uptake was undetected). Verapamil, given iv (200 micrograms/100 g BW) or ip (1 mg/100 g BW), reduced tissue 45Ca uptake by 50-90% within 2 or 10 min, respectively, and then its inhibitory effect diminished rapidly and was not seen after 20-30 min.
- OSTI ID:
- 6611284
- Journal Information:
- Endocrinology; (USA), Vol. 127:1; ISSN 0013-7227
- Country of Publication:
- United States
- Language:
- English
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CADMIUM
BIOLOGICAL EFFECTS
CALCIUM
BIOLOGICAL FUNCTIONS
TRIIODOTHYRONINE
BIOCHEMICAL REACTION KINETICS
ADIPOSE TISSUE
CALCIUM 45
CELL MEMBRANES
DOSE-RESPONSE RELATIONSHIPS
HEART
LANTHANUM
LIVER
MEMBRANE TRANSPORT
MYOCARDIUM
PORINS
RATS
TRACER TECHNIQUES
ALKALINE EARTH ISOTOPES
ALKALINE EARTH METALS
ANIMAL TISSUES
ANIMALS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BODY
CALCIUM ISOTOPES
CARDIOVASCULAR SYSTEM
CELL CONSTITUENTS
CONNECTIVE TISSUE
DAYS LIVING RADIOISOTOPES
DIGESTIVE SYSTEM
ELEMENTS
EVEN-ODD NUCLEI
FUNCTIONS
GLANDS
HORMONES
INTERMEDIATE MASS NUCLEI
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
MAMMALS
MEMBRANE PROTEINS
MEMBRANES
METALS
MUSCLES
NUCLEI
ORGANIC COMPOUNDS
ORGANS
PEPTIDE HORMONES
PROTEINS
RADIOISOTOPES
RARE EARTHS
REACTION KINETICS
RODENTS
THYROID HORMONES
TISSUES
VERTEBRATES
550201* - Biochemistry- Tracer Techniques